Having regular erections and using these erections is healthy for erectile tissue. There are injuries during sexual activity that can lead to erectile dysfunction; however, that is very uncommon. There is something called the refractory period where, after orgasm or ejaculation, our bodies enter a period where physiologically it is difficult to obtain another erection. This period increases as we age. When you're young, it does not take long to generate another erection after orgasm or ejaculation; as you get older, this period lengthens in time, and you will likely have to take longer to be able to obtain an erection.