Personally I found Dot-Tune good but unrepeatable. I got different results but it may have been because of environmental conditions as I did it outdoors. The last time the author (Snapsy) at FM said he found the best results using his method at infinity. He would use rooftops, street signs, etc. Not sure if that is current. If you read those articles there is mention of inconsistency but others love it which happens with other methods. If it works for you great.
I usually redo the MFA each spring. I do find variation, but it is just a couple of points. Any time you do measuring of any kind, you will get variation due to chance.
There can also be the issue of AF inconsistency due to the lens, but that is a different issue!