That depends entirely on where you host it. My PC has more downtime than GitHub does. It's only up enough to push to it ~75% of the time (I do use it as a ssh remote fwiw, but most projects get pushed to a VM that only starts on login, and my PC itself isn't always running).
If you're working on an oss project (ie distributing source anyways), probably better a good idea to mirror to GitHub as a backup anyways, let Microsoft pay for backup+bandwidth for you.
If you're working on an oss project (ie distributing source anyways), probably better a good idea to mirror to GitHub as a backup anyways, let Microsoft pay for backup+bandwidth for you.