Whither Extend Spell in 3.5?
Well, I guess people just have to decide if the ability to extend Endure Elements, Energy Buffers, Mage Armors, Greater Magic Weapons (?), Unseen Servant, Undetectable Alignment, Phantom Steed, Nondetection (maybe if you use improved invisibility a lot), Detect Scrying, and, at very high levels, Mind Blanks, is worth spending a feat. I would guess the answer is "no."Unless changed, extend spell would seem to have very little forseeable use in 3.5.
It's not useful for round/level spells (except at 1-3 level, they usually last all combat anyway).
It's only useful for minute/level spells if you've nothing better to do with the slot (my 3e Fighter/Abjurer/Spellsword used an extended Shield spell but that was only because his 2nd level abjurations were never useful to him) and 9 times out of ten, that's not the case.
It's not useful for 10 min/level spells at all. They already last long enough to last through an extended assault but you can't extend them long enough to last all day.
It's very useful for hour/level spells and quite useful for day/level spells too but, from all appearances, there aren't very many of either left intact in 3.5e.
If extend spell increased the duration of a spell by a factor of one--rounds to minutes, minutes to ten minutes, ten minutes to hours (possibly stopping there or just doubling hour and day/level spells)--it would be useful.
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