Too old, it appears to be the case now that there are no guarantees. Forward planning is thus made difficult. To avoid disappointment involves planning for the worst, but hoping for the best, and expecting the unexpected.
May I say, with such a definite mindset to leave in 8 years time, are you actually enjoying your (one) life? It's not a rehearsal, and if in 6 years time you're on a bitter slog to the end, just as they pull the rug from under the pension scheme, how would you feel? Like this:
Have a think. If the rewards of leadership stemming from promotion don't float your boat (they're not for everyone), then the lack of cash that is affecting the military is making it a very average employer, at best. The opportunities for AT and decent exercises have been badly depleted. Professional reward is abundant due to the sandpit, but again, give it a few years and we'll all be moaning there's nothing to do but pull up a sandbag and listen to bore stories.
Sorry to sound so glum; I'm not trying to encourage you to leave, more trying to check that staying in will result in happiness!