Question about engine oil and filter change intervals

This is on the Hitachi EX270LC with a Hino engine. I'm running synthetic 15-40 engine oil and Hitachi filters. Recently, the engine filter bypass light has come on when starting the machine cold. It's been dropping to about the freezing point at night lately. The filter bypass warning light stays on for a minute or two until the machine warms up a little. The engine oil pressure light goes off immediately, so I wasn't too worried about the other light staying on for a bit. So I assume one of the oil filters is getting restricted and bypassing. Does anyone know which of the two oil filters is connected to the engine filter bypass light? It has the screw on filter on the engine and the larger remote filter located in the corner of the engine bay. Also, how often would you change the engine oil when running synthetic oil. I thought it would go 500 hours, but maybe that's too long. It's just over 250 hours now since the last oil and filter change. (Last time I was waiting for the larger remote oil filter to arrive, so just changed the screw on filter.) Likely time for an oil change and to change both filters???