I've had a few posts on the subject lately, but I'll sum it up: Meta-game the crap out of it. Build at WBL at APL, but subtract duplicate items from New PC's wealth(and either just say the old gear broke when they died, or ensure the new PC receives the old PC's gear).
Especially with AP's, it's a hassle to adjust treasure, so rather than have to worry about that just keep the influx of wealth on the downside. That's my 2c anyways.