Ignition coil failure

Hello folks and thx for membership.

I own a mk2 blowing the ignition coil.

Im currently on the third in one and a half year and I cant find the culprit.

Plugs are fine, gaps within spec, distributor and contacts are a bit worn but not excessively, leads are fine and clean, cables are good and ground connection is good.

Alternator deliver 14V.

It runs fine on a new coil. After a couple of month the engine starts stuttering. No all the time but sometimes. Then after days or weeks it suddently stalls.

Waiting an hour or so the engine will run again.

This usually goes on for a couple of weeks and then the coil wont come back to life.

Any advise on troubleshooting?