As [KNF] we sieged a base for more than 7 hours. And that base had about 4800 basic alloy to begin with, which is considered few repair materials. It had enough H-fuel for the whole time, all we could do is the hits that trigger the shield.
Your base was not supplied so it was lost - it's not easy to take down a base. Get 2 defence platforms, stocked up with a nice amount of repairs and fuel for shield (preferred MOX or other stuff that are consumed in 2 units per 10 seconds) and viola, you got an immortal base.