no-win situation, and it wouldn't surprise me if it was a bit manipulative. Bob sounds like a nice guy, he has been helping her for years and years for free, so she knows he isn't the kind of guy who will ask for much if anything - however, if he does state a price, he will now most likely feel he needs to continue to help with the investing. Bob will most likely never ask for an amount that would make it worth it to him to keep going, but any gift from her could make it potentially awkward for him to stop.

So if I were Bob and was ready to get rid of the stress involved with helping her, I would tell her I don't want a gift at all, but then also tell her I was going to stop and give her a date where the service will end. If I were Jill, I would wait until after the time was over and then proceed to give Bob a gift she feels is enough to show her thanks, and then find someone else to help - being grateful for the free service for the years it lasted.