Personally i don't see any entitlement in the OP. Frustration and exasperation, yes.
I do think there is scope for a mix up here between posts saying "men should last longer and do more" and "my man has been asked to do more occasionally but wont/cant/doesn't understand".
The hope is, especially in a long term relationship, that 2 people will come together and more or less match in sex drive and style most of the time. There are millions of different sex drives and styles. And yes, each person will fluctuate from week to week too.
It's a big ask to promise to have sex with only one person for the rest of your life, and if it's wrong between you - it's going to fester. Recognising the usual peaks and troughs for what they are is important i think. Sometimes it is a simple matter of logistics - kids around, tiring work schedule, got into a rut etc. However when you see a pattern emerging over a long time. and despite trying things are not improving, it can feel like a bad thing to 'make an issue' of it. As winter found with her DP. Faced with the choice of a clumsy conversation which may not be well received, or carrying on with the status quo, it can be easier to keep chickening out of the 'talk' and carry on fretting :(
I'm wondering now if my DH suffers from premature ejaculation to some extent. Perhaps this, coupled with a natural tendancy to rush at things (he bolts his food and has is not good at being patient with 'fiddly jobs') means that he just isn't good at imaginative sex.
In reference to love's post about vanilla sex, and trying something different forcing dialogue, i agree. We 'play games' a bit. He likes to tie me to the bed sometimes for eg. There's been a bit of 'nasty sex'. Name calling/biting. The latest one is DH pretending to break in to the house wearing a balaclava. My idea 
. He was happy to do it and it was a laugh. So he can see the fun side of sex, as well as the race to the finish line.
IrnBru it's interesting that you say you have no problems and also that your partner has suffered with retarded ejaculation - having to work to get to the point where he ejaculates after as little as 15 minutes. My DP works hard to last as long as 15 minutes. Add in the fact that a good position for me is a dead cert. for him to come within moments.
mercury once, when DH took a particularly quick quickie and i had been expecting a bit more, i threw a strop and said something along the lines of 'oh great you're done then! How would you feel if i came and left you high and dry and went to sleep'. He got cross and said 'oh whatever', which left me seething. Then the next day he apologised for the quickie and the 'oh whatever', and since then he has been a leetle bit better in terms of thinking before letting himself finish.
It would be interesting to see any input from a guy here who has had trouble 'lasting' and being creative.