We’ve had this issue lately and I try and be reasonable but first I was abused by a newly moved in, drunken neighbour when I explained we weren’t the type of building where empty pizza boxes were left outside after consuming (we’d already put up with empty cardboard removal boxes which stayed for a week before our cleaner was directed to remove them).
Another neighbour kept their child’s stroller, same child’s push-tricycle plus occasionally other kid toys, together in a disused space under the stairs for weeks, even though their own, private lock-up garage was but 20 metres away.
Eventually, the committee asked them to keep the items in their garage in the most polite and sensitive way. But their reaction was extraordinarily aggressive and the items were left there making enemies unnecessarily with most owners. So the committee (presumably) had them removed, though they could’ve been stolen; there were many different tradesmen working in our building that week.
Consequently, my view is generally zero tolerance is best. If a pram is there for a couple of days a week, fine. But imagine if resident in our block of 36 wanted to leave their ‘goods and chattels’ under the stairs.