Bearing Seals

[sycraft]

I have a couple of small idler pullys and want to have spare bearings for them, as they are not readily available. I can press new bearings in a short time without the need for the whole pully if needed. They currently have rubber seals, but I am concerned with heat, these spin fast. I can get metal shielded bearings which have a higher heat capacity, close to 450 degrees, vs rubber at 240 degrees. I know rubber provides better sealing, but in the location they are, very little will get on them. What do the experts think...