What's the professional way to raise this vent?

I like the vents as high as possible, but that's just one of my quirks is to keep it up out of the water.

You could use a close nipple and a union coming out of the tee to make a replacement easier.

like @EBEBRATT-Ed said, i'd put a union in there right off the main so you can pull the whole thing down by just breaking the union but other than that nipples and couplers are the way to go. I think there is even a male-female union that could thread directly in to the main and eliminate the nipple there.

you can remove the close nipple with an inside pipe wrench or sometimes you can grab it between the sets of threads with channelocks without damaging it. you certainly can remove it with a pipe wrench but that is likely to damage the threads.

Just make sure that you don't have water hammer, and you'll be okay. If you have enough water hammer to damage that valve, then you have bigger issues than valve replacements.

I know you all must get sick of me asking questions, but why would there be water hammer in the main?

Agreed. Deal with the underlying problem and not with the symptoms.

If it is doing it at the start of a call for heat, it could be as simple as needing to hoist up that part of the main due to a sag that is holding water.

That's the only thing I can think of, in fact, that would cause water hammer in a main, and that was the reason for my question, which was not yet an argument (haha)—I was honestly curious if anyone had any other causes for water hammer in a main because I haven't experienced or seen it yet.

Even crazy carryover in my old boiler never caused hammer—it just caused gallons of boiler water to flow through my main and to the wet return—that is something that could potentially foul a vent, but as @STEAM DOCTOR said, that's a problem that should be addressed regardless of how high your main vents are.

My question was really about how I keep hearing about "water hammer hurting vents" but I don't know what that means. Do people have water hammer at the end of their mains?

It's a shock wave, due to the fact that there is approx. a 1,700x volume change in going from liquid water to steam and vice versa. If it is severe enough it is audible. If it is severe enough it can do damage to vents, especially the float.

I heard it in this system 21 years ago when I first moved in. My varivalves weren't damaged by it afaik probably since they are only at the radiators, but it was quite disconcerting. My longest main had a large puddle at the last 6 ft or so of it, due to incorrect pitch. I also didn't have enough downward pitch in my dry returns. My main vents aren't at the 180 deg turns into my dry returns but are at the end of the dry returns by the boiler.

People word things wrong sometimes. The reality is that raising the vent helps prevent damage to the vent in the case of water hammer.