Not necessarily. Jamie is still ranked top 100 in the Doubles. If he enjoys playing, then why not carry on playing. So what if he doesn't win often.
The worse thing that can happen is that he can't make ends meet and Andy can help pay for the travelling, expenses, etc... Andy is much more than rich enough to help out Jamie. That one single USO win will be enough to last them both for years before counting the £20 million+ endorsements per year that come from being a GS champion
Personally, I think Jamie will do alright, staying around the top 50 level. He needs a little topping up in the points by playing and winning with Andy once in a while. If he gets a little down, a few training sessions with Andy and his team will quickly raise his level and fitness !