Perfect dragonite with perfect moveset (gen 2)... Max out it or not?

Definitely keep it!
But power it up slowly if your resources are low/limited, but Do you have other high lvl Dragonites already?

I've powered up less good things than a perfect Dragonite and regretted very few of them. YOLO!

Assuming you want to bring it to level 30, that would bring it to 3070 CP at the cost of 120 Dratini candy and 119600 Stardust (thanks to GamePress's CP calculator). I think I would wait for another one. I would definitely take a less-than-perfect one at level 20 over that.

Wait till you have enough dust and Dratini candies to power it to at least L30 right away, then power it up. For now, leave it as it is.

i consider DB / DC the best moveset, being DT / O a close 2nd, i would try for 1 month (with eggs and near beaches) if doesn't work power up to lvl 30 :)

High IV mons are mostly for bragging purposes. Doesn't make a lot of difference in combat, that would upset noobs who haven't got the patience to find one with good IV's.

So just brag about it to your pokemon mates

It will only take 41,5000 dust and 56 candies to take it to level 20, so that is the extra cost to power this one up over a lesser level 20 Dragonite. There is absolutely nothing better to spend dust and Dratini candies on, and you'd be crazy not to power this one up. It is still the best pokemon in the game.

And it's not as though you're likely to find a lot more wild Dragonites. Even if you hatch or catch a high-IV level 20-30 Dratini, you will still have to spend 124 candies just to evolve it.

I powered up a perfect DT/O Dragonite from Level 10 to 40. At the end of the day not much difference between yours and mine. I even had a few Lv 30 80ish IVs already. Go for it. What's the worse thing that can happen? You have TWO powered up perfect dragons?

Do justice to a perfect Dragonite and power it up to the max. The requirements for stardust and candies from lvl 3 to lvl30 is minimal as compared to those from lvl30 to lvl 40.

My perfect Dragonite was stuck at level 10 for the longest time because it had SW/Hu. I maxed it out pretty much as soon as I got a fast TM to use on it.

Consider this: It takes 44600 dust and 54 candy to take your Dragonite to level 20. From there it takes 225000 dust and 212 candy to max it out. The cost to get it to the same level as a hatch is relatively low considering how much maxing takes.