Lengthening Low-Tech History

[Sindri]

A lot of fantasy (And speculative fiction in general.) worlds have histories that are with respect to their length given the tech level rather... exaggerated. There is a good reason for this of course. More history (Not more years, more history.) is generally better than less history.

Of course speculative fiction is in love with means of messing with tech level to best approximate the desired mix of technologies while maintaining other factors so a lot of ink virtual and otherwise has been spilt on the subject that doesn't need repeating here.

My question is: before taking into account technology crashes, deliberate suppression or situations leading to lack of incentives for specific innovations and similar methods used to mess with technological development how slowly can technology advance while still making progress (From TL 1ish to TL 4ish say.) with the various combinations of bad luck, bad surroundings and cultural factors that slow development.