how long to run in rebuild?

Hey guys,kwik question(google was fruitless)

How many Km's untill rebuilt engine is run in?( i get diffrent specs from diffrent ppl)
also, is it okay to bost a little every now and again, for short bursts(keeping things well under 5000rpm of course)

i have about 1200km so far. 😕

i normally do about 1000k's without giving it stick,if everything like timing and fuel is sorted it should be fine.