My thinking is that there are sooooo many easy, cheap or free ways to generate some points, it's hard for me to imagine ever actually buying any directly (speaking generally, not about Hyatt points specifically). Indirectly, sure. Or maybe spend them - remember that what you almost always need to keep points alive is activity, which could be either gaining or losing or sometimes transferring in some points (from some other place); sometimes there are creative ways to extend the life of points that don't require a big out-of-pocket cash expense (not saying I know of one for Hyatt, and every system is different, so check the rules carefully - for example, I'm pretty sure that one can transfer points from Chase Ultimate Rewards to Hyatt, though I don't know if doing that will reset your Hyatt points expiration date).
I am pretty active in playing the points 'n miles games, though I don't treat them all equally. There are some programs I find very useful, others not so much. Honestly, I've not found it worthwhile to traffic much in Hyatt points. I have an old Hyatt credit card that I barely use. I pay the annual fee and get a free night certificate every year, which I sometimes find useful, so I can justify the annual fee (although just barely). I know plenty of people love their Hyatt stays, I just prefer different currencies (for hotel points, I'm much more interested in IHG points, which I usually find more useful).
In any case, don't kick yourself if you broke down and threw a few bucks at Hyatt to keep your points alive. Find a way to use them on an upcoming trip, you come out ahead, and don't look back.