While it's possible to overdue it , the "1 dose per 3 months will not do so as long as your volume and dosage is correct.
Remember that at the end of the fermentation you will normally rack from bucket to carboy, then typically in about 2-3 weeks you will rack again as the finer lees settle out. At that second racking do not add more K-meta.
So Ideally this is the schedule I would follow:
Prep the wine K-Meta Pre ferment,
Start Ferment
Rack at end of ferment & add K-Meta
Rack in 2-3 weeks to remove finer lees - No K-meta
Rack 3 months from end of fermentation & add K-meta
Rack 6 months from end of fermentation & add K-meta
Rack 9 months from end of fermentation & add K-meta
Rack 12 months from end of fermentation, add K-meta AND K Sorbate , back-sweeten, bottle the wine
In some cases the addition of sweetening and K-Sorbate may precipitate out some residue or you may want to filter the wine before bottling. If you added a significant volume of sweetener you may need to use a smaller container for the excess wine.
Fining or clearing agents can be added immediately post ferment and then rack a little earlier than 2-3 weeks (Depending on the directions for the fining agents. Some folks of course add Bentonite at the start of Fermentation. Those are finer points that you just have to work out. I've got one wine - A peach wine - that still is a little hazy at 15 months from fermentation even with the use of bentonite. I filtered it but it still isn't ready to be bottled. I may hit it with one more fining agent before bottling but that's the sort of case by case decision process you just have to work out for yourself based on each wine batch.