Are you trying to just plane out get faster? or more of a question about keeping muscle mass?
for a faster time.. you should put some sprints into your workouts
I am not sure your work out schedule but if you are running long distances everyday I would suggest maybe a few days out of the week working on your quarter time.
and your 800 time this would help speed up your pace. and resulting in having being able to hold a fast pace for a longer time. the 800 would not be a sprint but you should time yourself and keep trying to beat your times on these..
do you run on a track? and do you know your times, like your quarter split?
do you have a time goal you are wanting to reach?