Lube system maintenance is one of those things that looks simple on paper but gets messy in practice. We run Bijur centralized systems on three Komatsu servo presses and here is what actually matters based on 8 years of tracking failures.
Filter changes every 3 months like raj_pm said — that is non-negotiable. But the thing most people miss is the distributor blocks. Each block has a piston that meters grease to individual points. Those pistons wear over time and start under-delivering. We pull and inspect distributor blocks annually. A worn piston might deliver 60% of the specified volume and you will never know until a bearing fails.
Oil analysis is worth doing even on grease systems. We take a sample from the reservoir every 6 months and send it to a lab. Costs about $35 per sample. What you are looking for is water contamination and metal particles. Water means a seal is leaking somewhere. Metal particles mean something downstream is already wearing. Caught a failing slide gib bearing this way — iron content spiked 3x before we heard any noise.
One more thing: check your line pressures at the farthest point from the pump, not at the pump. Pump pressure can look fine while the far-end points are starving because of a partially clogged line or a bad check valve.