Remove "time played" as a factor altogether and instead of having smith skill being player based, have it faction based.
A similar idea might be to make it "forge based".
Go to a village. Buy a forge (300 gold, flat fee).
Tell the forge what to start making. You tell it to start making Heavy Round Shields. Initially, it's 5% off the price.
Every hour:
5 shields are produced
price reduction is improved by 1%
After 10 hours you'll be a 15% price reduction (and you'll have 50 shields).
If you order this forge to produce anything else, that item will start improving and your shield bonus will start to decay at the same rate. So you switch from shields to swords. After 5 hours your sword bonus is up to 10% price reduction but your shield bonus is down to 10%.
Basically it's "forge specialization". The more you have a forge make one item, the better at it it becomes. If you switch items, you start over.
You can have 1 forge per village. So if you want to fully equip your army all by yourself, you'll need at least 5 forges, meaning 1 forge in each of 5 villages. (Ideally, you do not need to stay to run the forge. You tell it you want 10 runs of Nordic Short Sword and then you can leave. Come back 10 hours later and it will be done, and there's your 50 swords.)
More likely, though, you'd be with your clan. 20 people based in 1 village with 1 forge each can outfit their armies fairly rapidly.