I mean, that is completely different situation if it's stuck there and their body is already giving signals that it should be taken out.
Our anus were biologically made to expel things, not to take them inside.
Using dildos repeatedly on long periods can end into injuries that will affect your daily life, like anal fissure or hemorrhoids. And if we go too far, it end into more permanet injuries like rectal prolapse.
If by any means you need to experiment in any sexual way with dildos, use lubricant and don't use them in long period times.
Also don't use those who are too big, our anus are not bottomless pits.
Have fun and use them healthy.