I was surprised at my recent college reunion the number of those retired from the military, most O-5.
I've recommended the same to my kids (use the Reserves if needed, but get the pension)
The military pension for new recruits is watered down now. This happened within the last couple of years. They have decreased the pension and added a matching (max 5%) Thrift Savings Plan (military's version of 401K). Fortunately I was grandfathered into the old system, so I'll get the regular pension. The problem is that most young servicemembers won't contribute to the TSP, just like most young civilian workers aren't contributing significantly or at all to their 401Ks, and they'll be left with a lighter pension and an under-funded TSP.
For reserve members, this is an especially poor option for most, because the TSP has the same contribution limits as a 401K or 403B, so most people are better off contributing to their employer's plan (if it's matching) because the average civilian job pays much more than the one weekend a month military does, and thus will generally have better matching.
For someone on active duty who is diligent at contributing as much as they can to their TSP, this is a good option. For me, it just didn't make sense, as I already max out my civilian 401K and get much better matching, so if I had opted in, all I would get is a lower pension. So obviously I didn't opt into the new system. They sold us pretty hard on it, and I know a few who very unwisely were convinced to opt in... and once you opt in, you can't opt out.
Congrats on the upcoming 20 year letter. Those 5 active years will juice that retirement nicely.
Thanks! The pension will be nice, but the Tricare for life (and other Tricare programs available until Medicare age) is really the best part of the retirement plan for me.