Please explain what you mean when you say "spin the filter off and top up the oil".
I can't tell by the phrasing if you're just saying you replace the filter more often than suggested and then ensure oil levels are correct, or what, exactly, the advice is pertaining to in regards to the engine.
@drewkaree .....I should have been more specific - apologies! Back when we used to build high performance engines we would actually change the oil after a hard run. When you have an engine worth 50K you are careful. This practice morphed into changing the oil and filter if we did intensive water skiing, tubing etc. for a week or so (vacation). Doing the two previous things showed us the value of a clean oil filter and fresh oil. With most "normal" boating use this is not necessary.
However, (finally getting to your question), we (friends and I) believed that just changing the oil at the beginning and end of a season was not good enough. Some friends would change all of their oil and filter mid way through the boating season other friends would do it several times. A high performance engine builder we knew said "Why don't you just remove the oil filter, which will take trapped contaminants with it, put on a new oil filter and top-up your oil?" He believed that doing so - with "normal" engines - would constantly remove contaminants and simultaneously "freshen" the oil. I have done this for at least 20 years now with many different types of engines.
How frequently you ask. My boating season is May to October. May - fresh oil from the previous winterization, Mid-July R&R oil filter top-up oil, Mid-September R&R oil filter and top-up oil, End October replace all oil and oil filter for winterization. Obviously this schedule can be easily modified if the engine has a period of heavy pulling or high speed use. It has been super cheap insurance for my friends and I over the years.
The top-up oil is added to the crankcase via the oil filler cap and a funnel and checked when hot. If it is low a bit is added. Remember always better to be a bit too low than too high.
BTW you might be interested in the following - this is NOT a "normal" engine!
My first engine build project, a 390 HP 383 that I put into a 1994 Rinker, a 19 foot boat running IMCO powerflow headers, GIL offshore tips, driving a blue printed Bravo I with drive showers and a blueprinted SS prop from Indiana Precision Propeller (which I think Yamaha bought-out a while back). This was a true sleeper that would run 70MPH on the GPS and won me a lot of free beers until the word got out. LOL
Remember....always heat your oil to normal operating temperature before changing it!