My current relationship is coming up to 6 years and not much has changed since we first met except for the frequency of sex. Only a couple of times a week now but we've got a nearly 4mth old.
Still say I love you all the time, plenty of cuddles and kisses and helping each other out.
We rarely fight although we do have some heated debates but OH likes playing devils advocate and I kind of like a challenge. Sometimes things get a little heated or passive aggressive if being in the car is involved (I was hit by a car and I am super cautious in one, he does all the driving as I can't , so my reaction can be a little over the top and insulting sometimes) but it always finishes with apologies on both sides.
That's not to say we don't bicker, there's plenty of stuff that gets on my nerves like leaving stuff where it lays rather than in the sink, wash basket or the bin but I have my moan.and it's done till next time.
I've had 1 other relationship that lasted 7 years and it was much the same for a long time except I was doing the work of 2 people. There was little give on her part. I like looking after people so I didn't see how one sided that was until after the fact. She found God and God apparently didn't like lesbians (didnt know i was bi at the time) so that was why we broke up. Definitely did me a favour as I don't know how long I would have been in denial.
Every relationship is different though, doesn't make it wrong if it works for you. If you're wanting the single life though, maybe it isn't. I couldn't imagine being without my OH, he very much is my other half, but at the same time I know I could cope if something happened.