I have not seen Adventure Time, so I can't make any comparisons.
That said, Homestuck definitely revolves around certain themes, many of them emotional. I don't want to spoil things too much, but a lot of these things are pretty timeless. I recently re-read Homestuck (i.e. in the past year), and it holds up well.
I will admit, there's definitely a value to having had been there to discuss, speculate, and theorize with others. It gives one time to digest and metabolize each update, a forced pacing that one might not get when reading it straight through.
But that's true for any TV show! Game series! Written fiction series (especially penny novels)! Or anything else that has a release cycle.
If you're interested in Homestuck, I wouldn't want "being late to the party" to be the reason you don't read it. I was late to 17776 but it was (and still is) a great read. (BTW, if you like Homestuck, you might like 17776.)
Very fucky storyline, complicated to understand. Timelines, parallel universes, etc.
It gets very meta, in good ways.
Genuinely funny.
Elation at having had successfully read one of the longest pieces of fiction in the human language.
Music that slaps
The majority of the story takes place in chatboxes (think AIM), which is relatable to me, as someone who spent a lot of time inside on AIM and not a lot of time outside.
Running gags, callbacks, and references galore.
A problem: The first few acts was a kind of text-based-game deal, with the author literally making updates in response to user submitted commands. This structure is apparent, and it does not age as well as the rest of the comic.
The direction and basis of the comic kind of shifts over its 7 year lifespan. This is pretty apparent even without being super invested in it like I am.
One problem is that the original flash animations are being deprecated, replaced with HTML5 when it can, or YouTube videos when it can't, which sucks because the pixel-crisp animations and YouTube's CBR encoding do not mesh well. Even worse, [S] Cascade, arguably the most important animation in Homestuck, is not properly accessible from the main site.
If you do get into Homestuck, let me know, I can find you the mirror that hosts the flash animations.
twovests wrote
Reply to comment by flabberghaster in Update: just drank a room temperature cup of coffee i made three days ago by flabberghaster
but after spending hours exposed to the air, he might as well just buy folgers ;v; it destroys the point of grinding ;v;
still far preferable to three day old coffee though