DaCostaBR: I must have finished full RPGs without ever using an item more powerful than the basic health potion because, you know, I might need it later. I know it's the last boss, but what if the game has a last
last boss afterward?
To be honest, I have been trying to get away from this mindset.
For example, in TES: Arena, I am occasionally using spell-casting items. I note that weapons of Lifesteal are pretty good, as they do 40 damage, heal you 40 points, and have a lot of charges. Also, since they're weapons, they appear above everything except armor (only relevant for plate armor users) and shields.
In Final Fantasy 5, I like to use the !Mix ability learned by the Chemist job, and I have also been throwing scrolls for cheap elemental damage to all enemies. (I do have a few self-imposed restrictions for that game, as mentioned above, but I do allow myself the use of items.
Also, playing SaGa 1 or 2 with humans forces you to use limited-use items, as there is no other option (*every* obtainable item except Xcalibur and the Aegis/Masamune MAGI has limited uses in SaGa 2, and you don't get the infinite use items until very late in the game).
On the other hand, there are some games where, late game, I manage to avoid using any resources at all. In Phantasy Star 3, it is possible to heal solely with infinite use items (the fact that there's an item (the Force Vest) with unlimited casts of the revive spell helps, as does the Royal Vest to reliably kill the user to heal the rest of the party). In Lennus 2, you can use the Revive spell (at high skill, revives with 9999 HP) to heal, and use the Sexy Dress (kills caster to restore 75% of everyone else's HP) to force a character to be dead.
Another thing I try to do is use abilities that many players tend to ignore. For example, in my current TES: Arena playthrough, I am playing a bit with Transfer Health spells. They're sub-optimal due to their lack of scaling with your level, but they still seem to be effective enough to be useful. (If I were a Healer, they would be a bit more viable, but I'm a Nightblade at the moment.)