I was comped once (AA, 1998, Platinum, on the basis of DL status). It was politely, but firmly, made clear that this was a one-time deal and I'd have to earn it on my own from there on out. (I did.)

My understanding from talking to other people and reading lots of related threads on these boards is that that's pretty much the way it is. If they comp you once and don't see you fly a lot, they won't comp you again. (If they comp you once and you do fly a lot, you won't need to be comped again.)

If you want mid-tier status with airlines you don't fly on much, and it's worth $1,000 a year to you, try to get an AmEx Centurion card. Or, if your company is big enough and you're important enough in their hierarchy, some airlines will give you status on that basis. If you think you might qualify for that, ask your corporate travel coordinator (if you don't have a corporate travel coordinator, your company isn't big enough) to take care of it.