Maintaining sexual attraction with your long-term partner is not a given, it has to be worked for. There will always be highs and lows (lulls!) but the lows can be mitigated quite a bit if the partner is aware that it"s something that has to be maintained. As long as both partners are aware that there WILL be lows, and its just part of our biological nature and such, then everything can work out just fine.
You guys who are looking at ayachamo like he"s a retard for marrying this girl, or saying he"s with the wrong girl or whatever, are just doing so out of ignorance. You"re either 1) lucky that you found someone who manages to naturally/accidentally/intentionally maintain your sexual interest long-term or 2) possibly have slightly lower testosterone or some other biochemical reason for making it easier on you or 3) something else I haven"t thought of just now. It"s not as simple as "well I just have more integrity" or whatever. You might, sure, but we"re all naturally wired to want new pussy. Monogamy is a choice and a sexual strategy, its not how humans are biologically designed. It"s definitely the easier choice/more beneficial in general though, that"s for sure.
Ayachamo, you just need to be aware that you"ll probably always feel this from time to time, and you need to figure out how to deal with it in your own way. Talking with the wife openly and educating yourselves would probably help quite a bit.