You would probably be fine to peak out at around 50 brainers plus or minus 10 or so. Early on put a brainer everywhere you can. Feed the the scattered brainers prisoners, almanacs, decrypted discs, pillow books, any short duration research topics. Let your dedicated research base focus on longer duration or essential research topics. In mid game build up 2 or 3 research bases (redundancy to protect against losing a base). Once the easy topics dry up, consolidate your brainers to 1 or 2 bases to focus on the long duration projects.