indeed it is possible to be infected for that long and not even realize it. odds are that neither of you have ever been tested to know who has what.
at this point, hubby needs seen and start a work up to find out what is going on and go from there. we'd totally be guessing as to what is going on.
grace
your husband really needs to get the area checked by a doctor next time the symptoms appear.
My husband has not gotten it checked out at all. And, yes, we have both had cold sores on our lips from time to time.
has your husband been to the doctor to get the area swabbed?
do you or your husband ever get oral cold sores?