some of my thank you notes i purchased from night owl paper goods (right here in Owlabama!)
No matter how you feel about thank you's, they are definitely viewed as a necessity when it comes to weddings. Older people especially expect them and if you think it will take you a long time to complete them, I would start with the older gift givers first (I didn't follow this and it came back to bite me).
I've definitely been to some weddings and given gifts that I never received thank yous for and honestly it didn't bother me at all. I don't know if that means the younger generations will phase out thank yous, but we rarely rely on written correspondence any more and some people even use the internet to send their invites. I love paper goods and thus would hate to see them come to an end.
I would never have dared to not write thank you notes (unlike my refusal to write Mr. & Mrs. John Doe on the invites, I pretty much stuck to that unless it was clear that the recipient preferred it), mostly because I know it is indeed appreciated and that there would be no way for me to remember which people I had already thanked in person.
Emily Post says you have 3 months to send a thank you note. Going by that I'm about a week and a half late on the last few (though the last few were mostly received after the wedding, not sure if that means there is an exception or not).
Just for comparison's sake for the curious, we had about 50 shower gifts and 50 wedding gifts to write thank yous for. How about you?
And just for fun, if the married folks will vote as to how long it took them to complete theirs: