Our lease states that we can check smoke detectors monthly to ensure they are working. Same premise as @Udayabagya Halim - they are by (or in) the bedrooms, so they give you visibility to pretty much the whole property. However, we've never exercised this clause. For one reason or another, the hubby is usually inside each of our 4 units quarterly, and from spring to fall is mowing grass 3-4 times a month. So he's keeping an eye on things.
Just tonight my husband was saying he's going to schedule an inspection for one of our units - it's probably been 5 months since he's been inside. In the last few weeks a towel has replaced the front curtains, and we've now asked the tenant has been twice to get rid of the trashy-looking towel and hang curtains or blinds (he says he has blinds, hasn't had time to hang them). So it's time to get inside and see if everything else is still in working order.
That being said, we encourage our tenants to call us about things that break, no matter whose fault. And they have. We're reasonable about what they have to pay for, and the time frame for paying us back (e.g - broken screens we'll fix today, you pay us within the next 2 months). I don't want them to be scared to call us. Our biggest surprise at move-outs has been drawer slides being broken, or a screen door not latching.
@Account Closed - Just write into your lease a monthly maintenance review to check mechanicals/electrical/smoke alarms/safety items. However you want to word it. Then utilize it as frequently as you see fit. Very few people are going to balk at it. They know landlords can come into their apartment. Give 24-hour notice of the visit.