What are USMC infantry deployments to Afghanistan like?

Aside from being bored, exhausted, frustrated and uncomfortable most of the time, you can also expect to be hungry, dirty, and not know much about what's going on. It's not all Fallujah and Marjah, even those two had a lot of the above listed things.
You can also expect to be very well trained to handle anything that comes your way and led by some incredible Americans. You'll hit the highest of highs and the lowest of lows. Oh yeah, and you MIGHT even get to do a little shooting.

If it's anything like the Army infantry it can be summed up with days on days of boredom, accented by moments of sheer terror.

Talking to Marines that have experience is best. Documentaries can help, if they are honest, but many are fluff and PR. Search for USMC documentaries and weed them out. Here's one from 2011 of G/2/5 and is worth a look. The Company Cmdr in this was later a recipient of the Leftwich Trophy for Outstanding Leadership, so he has his stuff wired. A Mustang and West Point grad. There was another from Iraq but I don't remember description. It had some good input from the BN Marine Gunner and others. It was in the zone and had live-fire segments. The most intense engagements like Fallujah likely won't have any footage and there are many different types. House to house, high-intensity, counter-insurgency and more, so don't use this as an example solely. Any deployment is tough. Hope this helps.

http://www.documentarytube.com/videos/marines-in-afghanistan-the-untold-stories-of-the-5th-marine-regiment

https://www.mca-marines.org/news/maj-benjamin-middendorf-honored-prestigious-leftwich-trophy

90% boredom 10% wtf

This is a very broad question. Everyone has a different experience in the military. There are many different jobs in the military. If you are infantry or personal services you will have a vastly different experience. Not everyone in the Marines go out on patrols and fight the enemy directly.

Better than Iraq anyday

well in 2010 and 12 there was a lot of time at squad, platoon and company patrol bases. No PX unless you were lucky enough to get the truck once or twice on the deployment. Everything by snail mail. Good times. Make sure to try to go in the summer time....

Non-existent since the marine corps is no longer deploying to afghan.

So the OEF template for Afghanistan is less Active Military Operations, and a total conversion to Advise and Assist. A good place to start is think how Army SF works with their Advise and Assist Missions. That's the New plan, Afghanistan is still a very active combat zone so there is kinetic fights, but The Plan for Afghanistan is to Advise and Assist not fight for them.