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.

Oct
Low-cost, fast and Safe - Poe4orbs offers the best Path of Exile ORBS
Poe4orbs low-cost, fast and safe Path of Exile ORBS is getting much popularity, thousands of people have bought millions of POE ORBS

Feb
poe4orbs:Path Of Exile 3.6 Synthesis League Revealed Details
GGG has published the information about new league Synthesis of Path of Exile through official forum. In PoE 3.6, Synthesis, players will meet a new NPC - Cavas. Cavas who lost his memory wander in Wraeclast. You need to help him find the truth behind his memory. Also you confront new challenge, new skill gems and new reward.

Sep
PoE 3.12 Heist Starter Builds
PoE 3.12 Heist has started, have you decided which build to play? Poe4orbs recommends several builds that are very suitable for starter. These builds can work pretty good with low budget and are very friendly to the starter.

Dec
Path of Exile Rarity bonuses can actually affect the rarity of the uniques you get
No what this means is you run a map and pay 4 poe chaos orbs or whatever it is to apply nemesis from zanas map device.

Dec
Shaper seeds are tier based
Farming a specific map doesn't increase it's drop rate, it will just narrow the layout down. The benefits are to the market though. More map trading probably.