I am wondering what file format people generally use when placing images (photos) into their designs.

I was taught not to NEVER use JPEGs, and to always convert everything in to TIFFs. (something to do with compression)

I have only recently discovered that you do not need to convert images to CMYK (for print output), as INDESIGN does this for you! Shock horror, why oh why did I not know this before!!

As long as the images are 300 dpi for print, does it matter if they remain as JPEGS?

(I've got a massive project coming up and trying to cut down any unnecessary time as everything has been supplied as jpegs!!!)