Not wanting sex as much as I did before...advice?

Me and my hubby have been married 8months now (been together almost 3 yrs). He was deployed for a year before we got married so we had ALOT of sex the past year (He got back last august)...but now I don't seem to want it as much. We still have sex about 2-4 times a week and I still do enjoy it but it's more like I can't get myself into the mood for it. Usually he teases me and fools around and gets me in the mood and I don't mind that and have never told him to stop or anything because I still enjoy HAVING sex..it's getting myself in the mood and wanting it myself without him initiating it (and no he doesn't mind initiating it he likes it). Is this normal though? That after so long you just kind of go "ehh" to sex? Also he's been working alot the past month so usually we are both pretty tired. And last night we had sex but he never finished and he always does (except maybe once) and the past couple times we have had sex it took him longer then usual to finish (or at least I thought so). Could it just be that when we do have sex it's usually a couple days in a row and so it makes it a bit tougher to finish? Since it's usually the days he has off. So is this normal? For both of these things (for me and for him?) Thank you!