it depends mate all engines are different on this toyota engine that it was happening two was blowing out the front seal i changed it 4 times for him second time i pulled the oil pump off cleaned up the crank and put a speedy sleeve on the crank as it did have a wear mark in the crank it was good for about 3-4 weeks then slowly started to leak then will end up pissing out.
THis one had a big sign as not only was it pissing oil out the seal but out the exhaust as well so not only was it burning oil but leaking it as well.
Just for starters give the engine a compression test just to rule out if its down one one piston some times you might get an engine that has got ring or ringland damage that you wont pick up be the ear and its pressurising the sump.
Other then that pull the front off clean up the crank see if its got and marks or burs if so hit it with emmery then a speedy sleeve if it is bad.
Just because it may read 100,000km doesnt mean its done that