I love my butt plugs, I have a couple I use regularly:
Tantus A Bomb (wearing this now :-))
&
Cocklocker Large Inflatable Butt Plug
But I cannot leave either in a long time before they start to feel uncomfortable, anyone else suffer like this, and has anyone any suggestions for something I can leave in longer?
I find the best way to ensure you have a comfortable buttplug is to buy something made from a really high quality platinum silicone. The flexibility of this material cushions the muscles as they squeeze on it.
Tantus are pretty good for this; my favourite buttplug is the Tantus Tulip, which I can wear for hours without concern. It has a 1.7" diameter at the widest point, but neck isn't too thick, so the muslces can relax a little once it's completely in, which is also key to comfort during prolonged use.