When things are easy to check it's not such a big deal. Example is our bilge watch system. We have a 10 position Hart Tank
Tender and didn't need all the positions so we just hooked up one of the positions to the forward bilge (in front of crash bulkhead) and one to the main bilge right next to the bilge pump. No need for looking in the bilge, we can just use the Tank
Tender which is in the chart house (pilot house) next to other important gauges. There in the chart house, we also have a separate light that goes on each time one of the primary bilge pumps on. There's a switch to manually turn on each pump there as well. If I want to see the bilge, it's easy enough in this boat to do so right in front of the engine compartment through an access door. I don't even have to bend over, I just open the access, shine the flashlight and see essentially the lowest part of the bilge right there.
Focus on bilges? We sail a restored 1931 schooner. It's
wood and in theory--be design--could have more problems than a
fiberglass boat with water intrusion. Because of our recent
rebuild, it doesn't work/move while underway and does remain dry. As an aside: Not all wood boats leak, only those in need of
maintenance or beyond the
service life of the existing hull. Similarly, not all decks leak, just those in need of
deck maintenance or on a boat with too much sailing-related working/movement due to need of hull maintenance. Though the bilges of this boat are dry except for water we get from the (intended) drip of the
packing gland, we check bilge levels frequently unless sitting in a slip hooked up to
shore power. Then it might be once a day to check. While underway, the on watch person checks the bilge with no less frequency than when they're writing a log entry because they're standing right next to the Tank Tender when writing the entry. Easy to check, it will be done. Hard to check, it is less likely.
The thing that will bring us a wet bilge is if we're in heavy
weather and we do not close the
thru hull to a particular bilge pump residing under the engine. We have two there (redundant) and one has a lower vent loop than we'd like but such is life when you have extra pumps and need a place for the hoses to go. We only close the
thru hull on it if in big seas though.
Other systems? Frequency usually minimum is once per watch period to check engine systems (if using the engine), look at the
raw water intake (often see little bits of trash in there or sometimes tiny fish) alongside our cat who likes watching the water swirl around (the intake filter is in the
head where it can be seen every time you're in there for that matter) and rigging chafe/sails etc. If we're sailing in heavy weather or challenging seas, I'm more likely to be looking closely at things for
leaks (e.g. around the chain plates, mast partners) than if we're tootling along on mill-pond-flat seas and light air.
At
anchor, we have boat position alarms,
wind direction alerts,
wind speed alerts, etc to help us out but we are pretty careful to walk around and inspect
anchor gear in use--looking for chafe, wear, "impending doom" of whatever sort might be in the mind's eye of the watch stander.
Otherwise? We wander around while underway and pay attention to what we're seeing. Use the binoculars to check things aloft, yes.
Some people notice things more readily than others do. Some folks don't leave the
cockpit or pilothouse so they don't see a thing. Some people just walk around their boat and see things out of sorts in a way that might lead to damage or wear whereas other folks can be doing an "inspection" and not see what's right there in front of them. You have to know yourself and what you're capable of taking note of. If you're the sort who doesn't notice wear, tear, dirt, shiny spots, whatever might give you an up-front clue then it might be best to train yourself to do regular and frequent inspections. If you've made it easy to inspect things, eventually the inspections will turn into walks about the boat
interior and
deck that won't seem like a whole lot of effort anyway. Hopefully you'll be noticing if something is moving, loosening, chafing, wearing, tightening, etc, just as you're doing your walks about on deck.
Best of luck.