I would go no more than nine years. I have heard of people pushing the replacement further, but that's a damned big hole in the boat if it fails…
Here is a link at CF where I talk about my saildrive boot and flange seal replacement:
> The Volvo is fairly simple, actually.
> There are 10 bolts in the lower unit: eight around the leg itself (safety
wired), and two more further outboard on either side of the flange.
> Remove the eight leg bolts, and loosen the two outboard ones. These two will
keep the leg from falling altogether as you loosen the lower leg away from the
upper one. Get hold of the leg and wiggle it loose, and then undo these two
bolts and drop the lower leg.
> I didn't get to see the entire upper unit removal, but what I did get is that
the Volvo has a three-point engine mount. You can loosen the aftermost one (at
the outdrive) and the two forward ones will allow the engine to pivot forward
enough that you can put a piece of 2x4 wood under it to lift the engine a bit.
Then the upper outdrive unit unbolts from the boat, and out it comes, boot and all
link: Volvo saildrives: learned something new - Cruisers & Sailing Forums