Ever see a points sale and think, wow, that looks like a bargain? Before you buy, there's one question to ask: What would you actually pay in cash for this trip? If a business-class ticket costs $4,000 but you'd really only pay $500 for economy, that $500 is the number that matters. We break down how to tell when buying points and miles makes sense, when it doesn't, and why a sale isn't automatically a deal.

Hilton's co-branded credit cards are also offering elevated welcome bonuses right now, and two cards in particular caught our attention with some of the best offers we've seen: the Hilton Honors American Express® Surpass® Card and Hilton Honors American Express® Aspire Card. We look at what these offers actually get you, from Hilton elite status to free night certificates, and whether either card belongs in your wallet.

TSA may also be getting closer to letting some PreCheck travelers bring full water bottles through security at airports with newer scanners, although nothing is confirmed yet. We explain what TSA is considering and what it could mean for your next trip.

Rove is a free travel rewards program that lets you earn transferable Rove Miles on hotels, flights, dining, and shopping using the credit cards you already have.

The real standout is hotels. Book a Loyalty Eligible rate through Rove and you can earn Rove Miles alongside your hotel points and elite night credits. Departure Digest listeners get a 1,000-mile welcome bonus instantly upon joining.

Plenty of museums run free admission days. It's worth checking the calendar before you buy tickets.

Have a travel or points question? Submit it here and it may be featured in a future episode.

Some people like shopping. I like buying points. We all have our things.

The problem is, a good points sale can make it very easy to convince yourself you got a deal when you really just bought yourself an expensive problem.

This is Departure Digest.

We’ve got two Hilton offers that caught my attention, a reality check on buying points and miles, and some promising news about bringing water through airport security.

If you just heard “Hilton points” and mentally checked out because you never stay at Hiltons, give me 30 seconds.

For a limited time, the Hilton Amex Surpass Card is offering up to 130,000 Hilton points, plus a free night certificate, after spending $3,000 in the first six months.

That free night alone can be worth much more than the card’s $150 annual fee. Other perks include automatic Hilton Gold status, which can mean free breakfast or daily food and beverage credits, potential room upgrades and late checkout, plus up to $200 in Hilton statement credits each year.

And if you want to go bigger, the Hilton Honors American Express Aspire Card is offering up to 200,000 Hilton points after spending $6,000 in the first six months.

The Aspire has a $550 annual fee and automatic Hilton Diamond status, which comes with even more perks, plus a free night certificate every year and up to $400 in Hilton resort credits annually.

This free night award can be used for a standard room at basically any Hilton property around the world.

For example, the Waldorf Astoria Beverly Hills can cost over $1,000 a night, or you could use the certificate at a place like Topping Rose House in the Hamptons.

So if you can turn a card perk into a night at a hotel that would otherwise cost you four figures, I’m listening.

There’s also a cool feature with these Amex applications. You can check whether you’re approved before accepting the card, without an impact to your credit score.

Both offers are around through early January. I’ll put the links below if you want to take a closer look.

And that brings me to buying points, because this is one situation where I think they can make a lot of sense.

Airlines and hotels are constantly trying to sell points and miles, and sometimes the math really does work.

Say a business-class ticket costs $4,000, but you’d never spend $4,000 on that ticket.

If you buy enough miles to book it for $1,500, you didn’t necessarily save $2,500.

That $4,000 was never coming out of your account in the first place.

Maybe you’d have paid $500 for economy. Maybe you’d spend $1,000 on premium economy.

That’s the number worth comparing against.

It’s also why I’m skeptical when someone tells me they got 10 cents per point on a business-class redemption.

But if you’d never have paid $4,000 for that ticket, $4,000 isn’t really the number that matters.

The same idea applies to hotels.

Hilton runs buy-points promotions pretty regularly, and the price I look for is around half a cent per point.

The Waldorf Astoria Park City can run about 110,000 points a night. At half a cent per point, that’s $550 worth of points.

During peak ski season, that same room can run around $1,500 a night.

But would you really pay that cash price?

If you would, then buying the points for $550 is a real savings.

If you wouldn’t, you’re not really saving $950. You’re just finding a cheaper way to buy something you weren’t going to buy.

The points have value, but only if you’re actually going to use them.

So my rule is simple. I only buy points when I already know what I want to book and the math works today, not because there’s a sale I’ll deal with later.

A sale on something I didn’t need isn’t automatically a deal.

Okay, switching gears completely, TSA may be getting rid of a small airport annoyance.

The empty water bottle.

TSA is reportedly looking at letting some PreCheck travelers bring full water bottles through security at airports with newer scanners.

The newer scanners can get a better look at what’s inside your bag, which could eventually make it possible to bring water through without dumping it out first.

Nothing’s confirmed yet, and it may start with a limited group of PreCheck travelers.

But I’m very interested.

Some European airports are already ahead of us here. Heathrow and Dublin, for example, allow liquids in containers of up to 2 liters through security.

So we’re not quite at the point where you can stroll through LaGuardia with a full Stanley, but we’re moving closer to that becoming a reality.

In the meantime, if you freeze your water bottle completely solid before security, you can bring it through as long as it’s still completely frozen when it gets screened.

The second it starts getting slushy, though, the normal liquid rules kick back in.

And that’s a wrap for today. We’ll chat soon!