When thinking about toys, fatigue becomes an issue mostly in the weight of a toy, and the way you might have to hold a toy. If youre shopping for a toy online, and fatigue is a concern for you, ask about the weight of the toy. Get something that you can easily put down if you need a break. There are always lightweight versions of vibrators, dildos, and other toys.
If you are looking for strong vibration but know you won't be able to hold a heavy electric vibrator long enough, you can use some pillows to hold a wand vibrator against you, or to prop yourself into a position that allows you to lean into a vibrator. You might need some help setting this up but if you have controls that allow you turn the toy on and off, you can play in privacy.
You can also have a wand type vibrator placed between your legs if you are sitting up. Because the vibrator stimulates a large area, even if it isn't resting exactly where you're most sensitive, the vibration is often more than enough for a good time. These vibrators are great for lying beside or placing between you and a partner if you want to use it during sex with someone else.
One safety concern is that if the motor is completely covered all vibrators will over-heat and can burn. You need to make sure you won't roll over onto the toy, or if you will that you have someone around who can help.
If you're considering a vibrator or anything else with a motor in it, be aware that if you accidentally fall asleep with a vibrator on you or in you, it can pose a serious burn risk.