Fighter Size in War and Peace

Question here is, referring to Ainuman’s post: Do air forces – with the financial and technical means to choose – tend to build heavy fighters in times of peace and lighter fighters in times of (prolonged) war, or is it the other way round – light in peace, heavy in war.
And if one includes fighterbombers in this equation, another way of asking might be: What is the operational value of expensive, heavy multirole platforms available in smaller numbers vs. cheaper, lighter single-mission platforms available in larger numbers? That question is as old as military doctrines and was very present e.g. in the airwar doctrines during the cold war. What is the influence of modern technolgy here?

I think it tends to be heavy/multirole in peace, light/singlemission in war.

Any comments from our enlightened community?