Plugging tyres is ok as long as it is not too close to the edge or the hole is too big.
I've used 2 different types of plugs and they both have had a good hammering and not let me down (No homosexual punns intended)
The first is a permanent repair which is done by a tyre garage which consists of a plug with a patch atached to it and the tyre has to be removed to repair.
The second is the type that the AA or RAC (others may use but I know for definate that these guys do use them) use which is a push through type without removing the tyre. They say it's temporary to cover their arse. I've done over a thousand miles on one until the tyre was worn out and had no issues with it at all regards losing pressure.
So you should be ok on both.