Cheap ebay compressors reliability

Don't let it get too hot and give it ample time to cool down between fills. If you can get an external fan blowing on/through it, that will help keep it cool and extend its life. I think the rule of thumb is don't exceed 60°C. I fill my guns directly so I rarely break 50°.

Aside from that, those compressors are generally throw aways. Use it till it breaks and then replace it. Some compressors like the Yong Hengs have rebuild kits and parts readily available though. If you're mechanically inclined, they are repairable.