Schlupp is getting on a bit I gather (33).
There was a good article in the Times which explained why PL teams will often only offer forwards one year contracts after the age of 30 with Salah being used as the main example. That does not mean Liverpool will not give him longer but it pointed out how it was more of a gamble. They looked at all the main strikers over the years and showed how their stats tailed off the older they got once 30 was breached. Ronaldo was interesting as he started doing very little but trying to score the older he got.
I get it, there are exceptions to the rule (Woods at Forest) and we are talking the Championship. However, we are no doubt talking big bucks especially if he plays as a winger. Slightly different playing at the back.
Big gamble at 33 I would feel as will want possibly three years and top dollar.