Among the various discussions regarding power level for spells, I thought of making a change that hasn't been brought up (at least that I could find) that should make spellcasters think about their spell choices when selecting spells to learn and casting spells thereafter. I'm thinking about changing most spell durations from the common 2 rnd / rank to concentration and provide additional scaling options for concentration + duration (after concentration is ended) and the typical 2, 5, 10 rnd per rank.
This change would cover most spells that are typically not combat oriented like invisibility, fly, force bands but exclude things like bladeturn, mage armor (and equivalents), attack spells or spells like merging.
To my thinking this shouldn't affect anything in a drastic way and make spellcasting more strategic in the game, but I'd like opinions of others to uncover any oversight in my thinking. So, what's your thoughts about the idear?