With the older rubber/brass bushings you could feel the play a bit from side to side if you pushed on the shaft below the boat .... but that was not a very scientific test since that much play clearly meant it was time to replace the bushing ... on the newer style, I am not surprised that you are going strong ... but I would probably consider 500-600 hours time for a preventative replacement.
You should check your shaft alignment with a feel gauge at least once per season also.
Some folks didn't realize that the drivetrain was in need of a replacement bushing until they actually do the replacement and the boat feels better.
Keep a tight line, and a smile on your face. Peace out.
2008 Prostar 214 MCX
Previous 93 Prostar 190 1.5:1 GT40
"Left Foot Forward and preferring girls."