There needs to be a separate Artificer feat/enhancement that allows the artificer
to extend those 5 min spells into 10 min spells.
However due to the nature of an Artificer's magic...I would alter it from the usual extend meta magic feat.
Artificer Arcane Extension - This feat will double the duration on any Artificer 5 min spell however
the spell points required will double as will the cool down to recast it.
so..ablative armor - duration 10 min, SP 20, cool down 2min
just a thought