95% of builds on Path of Exile scale with special uniques or powerful rares
The reason it is still fun after 20+ hours of play is because of the skill and gear progression that comes with most builds in the game. 95% of builds on PoE scale with special uniques or powerful rares as well as getting gear that has more linked sockets (5 socketed and linked sockets on gear are a lot more rare than 4 linked gear, and 6 linked gear extremely rare and endgame to acheive in most cases). Both of these will change will change how the skill works/increase their damage output significantly, making you want to progress even more to see how far you can take a build idea.
So the long and short of it is yes in it's most basic form the fun of playing the same skill over a long period is to see the returns of your investment into the skill and seeing how far you can take it, which is much more rewarding than it sounds due to the sheer complexity and number of options the game has to offer.

Aug
poe4orbs:[Lake Of Kalandra] PoE 3.19 Duelist Lightning Strike Champion Starter Build
This PoE 3.19 Duelist Lightning Strike Champion Build is a tanky fast mapper that works in SSF or leaguestart.

Nov
Eternal orbs still exist in standard
what we really need is to get rid of all the eternal orb influence in standard, or make a new dumpster league without eternals and eternalled mirror-able items destroying the market.

Jan
How to do Righteous Troll build in Path of Exile 2.5.x Patch
Chieftain with 9 endurances would have 13.5% regen not 15%. While chieftain would have more regen and probably a bit more damage, but he wouldn't be as tanky against physical damage.

Jan
What do you do when you have nothing to hit on a trap doing Uber izaro?
My Earthquake Bleed Poison Melt T15 boss faster than you burn Xoph and I'm Slayer 7000 hp. So I leech 30% of my maximum life every second all the time it's like 30% regen = leech 2100 per second.

Sep
poe4orbs:Path of Exile Blight Top Duelist Builds
r4pg also prepared PoE 3.8 Duelist Builds for players, including Slayer, Gladiator, Champion. Players can choose some as league starter builds.

Jun
Top 5 Starter Builds for PoE 3.3 Incursion
In this article, I will share you Top 5 Starter Builds for Incursion league, which is the main content of Path of Exile 3.3 patch, and you can have a really good beginning with these builds. Last but not least, you can buy PoE Currency from our website - it's the preparatory work to get into Incursion league.