Be past/pass one’s sell-by date = If someone is past their sell-by date, that person is not wanted or considered useful any more because they are too old.

• There is plenty of time to have a baby.  I am not past my sell-by date yet.
• The company is forcing my mother to retire because they think she’s past her sell-by date.
• That player is definitely past his sell-by date; he hasn’t had a good season in years.

Be stuck in a rut = too fixed in a particular type of job , activity , method etc and needing to change.

• I need to change my job – after 15 years here I feel I’m stuck in a rut.
• We’re stuck in a rut ; let us move abroad for the summer and shake things up.
• I had so many ambitions when I first graduated from college, but now I feel like I am in a rut.

Middle of the road = not extreme and is acceptable to or liked by most people.

• I am looking for a middle-of-the-road option.  I don’t need a high end TV, but I don’t want the cheapest one either.
• They adopted a sensible , middle-of-the-road policy on defence spending.