I'm guessing that you agree that there are only a select few instances in which a duration of 16 hours would have been enough whereas 8 hours wouldn't have (or any other duration, for that matter).
Realistically, then, you would mostly use Extend at the end of the day to start the next day still benefiting from those buffs. That's a fine enough use, but I don't think its benefits outweigh the benefits of Subtle Magic.
I'll still mention it in the thread though for anyone wanting to try it out.
I didn't think of that actually, that's a cool idea.
However, it's not like we hate having high STR. We want to have a decent attack so our Booming Blade OA is an actual threat.
Plus, paying an ASI is a pretty expensive price for just 10ft. of movement. I think I would prefer to just suck up the slow movement (Halflings make do with 25ft., after all).