What do the infinitives suggest about the action?

That it was a regular but not continuous activity.

For example,

I go to school. - most days, but I am not doing that now, I am at home.

I used to go to school - as above, but I no longer do so.

and so on.

The tense can change, as can the mood - when used with an auxiliary verb. For example, I should go to school.