Old infiltrators aren't so bad. In fact, I think that infiltrator is the one class that is affected least by aging in terms of hours. Sure, the skill decay is bad, but as far as time goes, it's not a big deal. If you're smart you'll do only one high risk option when there is no guard activity in a region, such as assaulting a high priority target, or doing the high risk burning. Then you get out of there. An old infiltrator can still function with the one hit then leave. I think the longest any infiltrator action takes is 4 hours, so as far as we know, all characters can manage that.
