It should be done.
First starter I ever did was done in 24 hours.
Last starter was old yeast....and took 3 days to finish 2 litre.....which was 2 different dme additions.
If it foams up when you stir the flask like a soda....then that is the CO2 coming out of solution......you should be good.
When are you brewing? Let it set without stirring over night and you should see a nice band of yeast covering bottom by morning...or within a few hours
Check out Revvy's comments in this post ...this was helpful to me.....