took a couple of easy electives. on a 6-week semester, that was all the load i could handle.
I took a couple of literature classes in the summer to catch up on my hours. Otherwise i wouldn't have been able to graduate on time.
I thought it was a good experience overall. Taking a few during the summer lightened my work load during normal school hours so I felt better paced - and I didn't have to move all my stuff out of the campus apartments.
It was more work, though. It was every day, instead of every other day, and my classes were online so it was constant reading and writing.
It is OK, if you have nothing distracting you. Traditionally, students might take electives in summer school because nobody cares about electives, anyway, except that they are required. You know. Foreign language courses; art and music courses. Stuff that is required but doesn't matter.
Last summer I took an intro to bio class(8weeks) it was approx 4 hours Mon-Thurs. I probably could have handled one more class maybe but it was intense. Anything over 8 would be awful hard. My $.02
I took summer spanish, it was 6 weeks and 6 credits, pretty brutal. Like 6 hours a day. But I really didnt want to take my foreign language and it at least knocked it out quickly.