How do you handle "mana" in a good way?
I want to create a system that uses it as a source of power for spells but I l'm not sure how to present it.

For example let's say there is a spell to enhance your strength.
How is it better to present it?

1= using this spell constantly drains your mana someone with a regular mana level could keep this power up for a whole day.

2= This power costs 1 unit of mana each hour, in this example let's say a regular mage has 25 units of mana.

Or in what other form could this be done?