Over watering can also stunt or kill your plants. It can cause root rot and it can also prevent them from getting oxygen which they need. I'm glad you've been lucky so far, but a solid watering schedule will also make your plants explode in growth and root structure. I wouldn't want someone ruining their money and time by over watering their girls. @Waira care to add any other advice?
My question to you on the subject. Its simple, what is your medium? Light airy medium that are soil-less, or contain tons of perlite will allow the water to move through the medium and most of that stuff does not retain the moisture levels actual compost does. Its the nature of the beast, if someone is using a soil based medium it will retain water way more than something that is peat based. So yes over watering can and will happen, i have seen it time after time, when someone does not have proper aeration in the soil and its too heavy.
FD has got it right! Overwatering in typical true soils is very common, depending on their amendments like perlite, if coco coir is a component (coco is one medium that overwatering is much less prone to because of it's inherent texture and properties), type of pot (breathability/evaporation from sides like in fabric pots), or content of clay/glacial dust, mushy mulches, vemiculite-- all of which hold water big time and make soil mixes heavy and retain water longer,..... gas exchange in the root zone is critical, and too much water will smother them and retard the process, hence the wilting! Also, it's can harm the soil microbes as well,...
... free draining media can shed the water in time, as long as it drains completely away, no back-wicking from a saucer... coco is famous for it's capacity to hold and release water due to it's springy-spongy texture,.. peat is not like this, in fact for my carnivorous bog plants, peat and perlite (and sand) are the medium of choice because it holds water so well,.. these plants literally sit in a shallow pan of water all the time! So peat-heavy mixes should be watered more carefully, and have plenty of perlite...
Master it though, and you can grow-
!
Well, part of it is how long it stays saturated to the degree that there's no space open for gas exchange; past 20 min. or so, it becomes more damaging... yes, some noob's end up watering the hell out of plant repeatedly, like they're water-boarding the poor things!
Watering to 10-20% run-off is usually a wise thing to do, especially if you're using synthetic nutes,... this keeps the salt build-up from getting too bad, and causing all manner of problems... any pot is kinda like a cone coffee filter: as water/nute solution moves down through the media, it increases in conc. of solutes... Organics it's not necessary, unless there's been a big overdose of something! In any case, keeping the pot from getting soggy bottoms or forming dry patches from inconsistent, uneven watering is always an issue... using a wetting agent/water spreader can help a lot with this, particularly with dry patches from media that's become kinda repellent,...
seedlings, it's a bit more tricky. Never let them dry to stress, that makes for stunters from root damage,... too much and you get potential damping off, and again, root damage from smothering; letting it dry a bit at the surface help force the roots to delve deeper, but that's a tricky juggle as a new grower, to learn how fast things dry, in different conditions, what to expect from changes in them, etc,... Personally, I try to keep things as evenly moist top to bottom, with some surface drying (not totally) down a inch or 2 depending on their size,...using a mister can help regulate your surface inputs, and not make the lower levels overly wet from rehydrating that upper layer frequently,...
:smoking: From what I see in Sick Bay, nute burn, bad pH management, and underfeeding are the major issues with noob's,... coco especially! so many think it's just another type of soil, and treat it as such... and end up having problems-- sooner, not later!
whaaahh?? I got a rep?! Cheers mate, thank you,... Coco is fantastic stuff, one just needs to lean about it's differences and properties vs soil and peat "soilless",... lots of good info here, and on the web of course.. Canna Coco is a good company, with coco, nutes, and a website full of good info, if a bit scattered... Coco has unusual Cation Exchange capacity properties, part of what trips peep's up when using it and not learning how to work with these sorts of things... 
Also, check out the Autopot section here too, many of those folks use coco for it, and are getting kick-ass results from a totally KISS system! 
