It very much depends on your clients and the nature of the traffic they send. For a high-volume client, assuming a default of 100 concurrent streams per connection max, this actually works out to <connection establishment>, <50 parallel requests>, <connection close>. Have to ~quadruple your connection count vs what you could have done on one unfettered connection, and every connection will spend 50% of it's time being established.

Some hybrid of count and time might do, e.g. `50 requests AND 1+ minute since establishment`. But it's nuanced - surprisingly hard to find logic that works well in all cases.