It depends on how good your players are.
Typically, I find I split the time about 50/50 with the players. This is not ideal, but it's reflective of the fact that the players don't really role play except when forced to interact with NPCs in character, which basically is a conversation with between me and them, usually with them asking questions and me giving answers.
The only time I spend long moments not talking I'm not actually sharing spotlight because most of my players when they are talking are planning, largely in an out of character stance what they want to do. But I don't feel this is actually game play and it's really dull.
Like I don't know about the rest of the GMs here, but when my players RP effectively together that's just a thrill. There is nothing better than just leaning back and watching the game for a while and being entertained by the players, needing only to throw in a few beats to keep the game going.