If you did two things, I think your players would be quite content.
1. Increase the crafting reserve from 2% (which it currently is) to 3%.
This is a pretty generous dose of exp to invest, and will probably be adequate for all but very big projects (see 2.)
And
2. Allow unspent crafting reserve from the last level (and *only* the last level) to be carried forward and used.
This second one prevents Artificers from dancing around with pained expressions, as if they need to pee. "Almost levelling? I need to craft! I need to spend my reserve! Wait, guys!" Being able to skip a trip back to one's precious forge would alleviate a lot of this urgency.
For really, really large and ambitious projects, there's always "Crack that, it contains vital Essence!" which siphons away many lesser magic items into your exp sink. And then you need just a little more..
After all, everyone should feel the need to get out there and adventure.
