Well we have seen what happens when you cut ties before a Kicker or a Punter has seen the live fire of a NFL game, it's much faster, with all the new players coverage and speed of the rush along with how fast he has to get the ball off and his steps. Placement, hang time, and then yardage. When your a team that the 49ers appear to be a Punter is the defenses best friend as well as the safety net of the offense.
The reason so many punters and kickers have long careers is because it's hard to replace them with good consistent mentally tough players.
Punters and Kickers are often playing will into their late 30's and some into their 40's, You say he seems to have lost something the last few years, changing stadiums, field position, types of Punts needed, or a direction from his coaches to hang more and give coverage time and less return yardage etc. You have to admit a lot of stuff went wrong and changed the last couple of seasons in S.F/S.C.