What's your best proxy setting to keep it live ?

I've 50 private proxies. 30 from buyproxies and 20 from solidseovps.

But the problem is after 5-20 minutes the live proxy will decrease to 35-45 . 

I've set 180 html timeout and 60s beetween search engine queries. 

Btw, i didn't use private proxies for scraping. Only submission,.