Question on Libations

I use small bowls to pour my Libations into, usually spring water. What is the norm for how long I should leave a libation out. I live in a apartment complex so there not a lot of open area outside to dispose of the libations.

I consume the libation from ritual as what is called 'prassad' in Hinduism. I "reverse" the offering with a prayer that I may consume as prassad what is left from the offering. I usually do this before the next meal, and drink the wine with it. I'm all for practicability

What is the norm for how long I should leave a libation out. 

Not long – for worship at an outdoor altar, it would be poured out as it was offered. For a libation into a vessel, as at an indoor shrine, it would be taken down sometime after the conclusion of worship, and before the next worship time.

As DeLi mentioned, you might also take down the libation vessel and imbibe it as a consecrated item – consuming what has been shared with God as a kind of blessing. 

If you do not have a suitable location to pour out libation offerings, it might be simpler for you to offer burnt offerings – incense or sacred plants, like leaves of laurel, myrtle, thyme, vitex, etc.