I know there's a such thing as being too polite, and I know that sometimes it can really get one some people's nerves. But on the other hand, never thanking anyone for anything every time is just rude. The same goes for apologies.

What're your thoughts on this?

My opinion is that it's much more annoying to not be thanked at all. Even more so with apologies.

I agree. Better to say thanks a few times too often than not at all. And better with ten apologies for the same thing than not a single one.

Apologies and thank-yous are both needed just once, so long as they are sincere.

I will get irked by someone not being thankful, but not saying it at all could potentially infuriate me.

It feels insincere when you get a gushy thanker. I worked with one who'd do it after anyone took a message for her and dreamed of locking her in the file room after a couple of hours each day. Still twitch when I hear thank you said more than twice in a row.

Repeated apologies though depend on the situation. I had a car accident once, low speed, my fault entirely and I was so shocked and horrified I couldn't stop saying sorry. It went on for about 10 minutes then I just started crying my eyes out. I know what you mean though, it's the ones where they keep coming back and doing it that make you just want to tell them to just shut up already.

Ya I think thanking is better than not at all.

I'm usually holding doors open for other people and in school I just walk forward holding the door until I feel someone else behind pushing it. I rarely get thanked (Only by elder people ''Thanks, young man!'') but I just thank myself in my mind, to not feel unseen.

But, to the topic, which I actually wanted to respond to:
Thanking too often is better than don't thank at all.

I'm am a proud over-thanker! (My new word!)

I practially bow. I'm always holding doors open for people. Half the time whomever I'm with gives me the evil eye because I'll stand at the door for like ten minutes. If I was rich I would pay for peoples purchases ahead of me and I always offer to help the elderly or disabled when shopping if they can't reach something, dropped something, etc. I'm a firm believer in the Golden Rule and will go out of my way to assist.

I'm a complete please, thank you, you're welcome and have a great day kinda gal!

While I feel that thanks and apologies are a matter of respect, I can't help being lenient about it. I automatically feel thanked or apologised to if the person's expressions or actions show the associated vibe. I can always tell if someone's being insincere or plain rude, therefore people who aren't forgetting on purpose never really bother me. The last time someone over-apologised to me I ended up thinking I wasn't sure if I could bear to be friends with her (there were other reasons, namely what she was apologising for). A lack doesn't disappoint me so much as a careless attitude to the thankfulness/apologetic relationship we have at that point in time.

Apologies and Thank You's need to be said, but when people keep on saying them, it does get annoying

There's a coworker who drives me home every night. It's directly on his way home so all he as to do is pull over and let me out. I thanked him each night initially. Now I just thank him every once in a while, because...do I really need to say thanks each and every night? I think if I did, it wouldn't be sincere anymore. But sometimes I feel weird saying, "Alright, see you tomorrow! Good night!" without a "Thanks!" I don't know. I wonder what he thinks about it, whether he cares. Does he expect a thank you every night? I can't imagine. I think he'd prefer not to be thanked every night. He knows I appreciate it... and I plan on getting him an Xmas present for all the drives he's given me...What do you think?

I always say 'thank you'. I don't really say 'please' - a part of me says that it's a waste if they say 'no'.
But about others - I think both are just as annoying. On one hand it becomes meaningless if they just hand manners out without effort or consideration for what they imply, the other is slightly offensive.