Suggestions and a little... bug?
Sometimes, in a depth with 2 closed doors, one of the keys is inside one of them. If you find the free key and open the wrong door, you will never open the second closed door.
Suggestions...
First, congratulate you for the long life of your game, is extremely re-playable, i've played the game hours and hours and i'm not bored of it yet. Congratulations!
But i think... another class, or races, or little powers after each boss (stats, or things like the existing ones) will improve the game lenght.
Warrior? Human or Dwarf (Dwarf search auto hidden doors better, but moves a little slow, or uses maces, hammers and axes easily...
Mage? Human or elf (Elf starts with -5 hp an -1 str, but recharge wands faster and increases damage with wands, shots faster or more accurate...)
Rogue? Human of Halfling (Halfling moves slow but hides like a natural +3 shadow ring and find more gold, or better buy/sell ratio...)
Another class? Bard (With a item, "mandoline", works like a wand and can play "lullaby" or "Terror", but sometimes fails and cast "Challenge" if casts Terror)
Maybe Paladin, Monk... more possibilities, more lenght...
"The better, if longer, twice better"
After kill goo, you can choose between little bonuses like more max HP, +1 Str..., after kill Tengu, the book, after kill DM300, another bonuses like the goo, and after dwarf king... ¡Another book!.
You know, different progressions, variations, etc, not only the 'map luck', more and more different replays...