Plugs, yes, should be free as they are meant to be temporary and last I checked were not supported by tire manufacturers or industry standards. I mean proper repairs with vulcanized patches from the inside. In my short stint as a dealer tech the guy in the bay across from me did a plug as a "courtesy" during other work and didn't tell the service writer much less the customer (that was far from the most unprofessional hack I saw him do).
Like music and management, there are some people that have the knack. In the shop, I saw about a person a year like you that had multiple plugs that that weren't leaking and more power to you. However 99.999% of people do not have the knack and I did proper patch repairs of leaking plugs several times a week. I got out of the arts because I don't have the knack and I tell others when they talk about wanting to go into the arts that hey, kudos if you can do it but it's hard and most ppl don't have the knack, etc.
The difference in the effect on the tire between a plug and a reamed out plug/patch is that the plug is if the user doesn't ream out the hole to be circular, the plug can wedge open the corners. Also that nowhere in the plug's length is it any wider so the only thing holding it in is friction, the vulcanizing goop (if the user used it), and a prayer.
.......Also take the time to rotate the air in your tires. That really helps!
If you put 15 lbs. of air in each tire instead of 35 lbs. you have lowered your unsprung weight by 80 lbs. overall.
I'm glad you reminded us! I'm still running with the air from last fall, I need to get it rotated ASAP!
Checked the air in the bikes today. I took out the flat, stale air and added fresh summer air.
A tire repair shop wanted to patch my plug because it was safer. It leaked. Next time I plugged a tire, I had it patched, for safety. It leaked. I prefer plugging my own, for safety.