"Don't know about everyone else but sometimes my guitar seems better in tune than other times and that's even after using a tuner."
I don't want to tell you something you already know, but are you stretching your strings properly?
Regards,
Bob
Believe you me Bob they are well stretched because they are never changed too often

Maybe that's the reason they go out of tune.
On the subject of strings I use Martin custom light, usually three packs for £10 on ebay.
Musiclover