Glad to hear being a STH doesn't suck and that this is more of a postseason problem. I have no clue if I'll do it, depends on where I'll end up this summer, but considering I went to 15+ games this year I might as well just spring for a 1/4th season. In the end it'll be cheaper and I'll have a regular seat.
It's not necessarily cheaper, for most games you can get cheaper seats on StubHub, however for the increasing number of games that have large crowds it is nice to have the plan tickets. The benefits of being a plan holder are significant, with the Red Carpet Rewards, the invite to the fan appreciation day, and the ticket exchanges, although the RCR are being scaled down this year. Of course the downside is that you lose a little flexibility in picking games at the last minute based on your schedule, the weather, and pitching match-ups.
I have the cheapest possible plan, 20 games with a single $10 seat in section 222, it's great because I get all the perks of being a plan holder for a minimal commitment. Another thing to look into is to split a plan with someone, I'm in another group where I buy tickets to a small number of games that gets me into the good seats a few times a year.