I still care about my customers but I've found that a lot of buyers ask a question and then disappear and don't check their emails for several days, so I don't answer as quickly as I used to.  If they really want the item they'll be there when I do reply, and not replying for a few hours won't stop them wanting it.  If it's a case of strike while the iron is hot, and before they lose interest, chances are they'll regret their impulse buy and want to return it anyway. 

Some ask questions and say they want something specific but when I do a special listing for them I never hear from them again.  So again, I don't get too fussed about answering straight away.  I often have to get stock out to be able to answer questions and it's hard work when people waste my time.

Like someone else said, answering straight away sets a precedent, but it also confirms their belief that sellers have nothing better to do than sit at the computer waiting for questions, so then they expect it even more.  Some would think an immediate reply means we have nothing else to do because we have no sales, and then they start to wonder what's wrong with our products.  Answering immediately might also make them think we're desperate for sales, and looking desperate is one of the biggest turn-offs there is.

If I ask a question on another website I don't expect an immediate reply, and if I get a reply within 24 hours I tend to think that's pretty good.  I'm talking about sites that could have a LOT of sales, not like a small seller on ebay, but the principle is the same.

I used to try and answer everything straight away but these days I might see a question in the morning and think, "it can wait until the afternoon", sometimes even that night.  For all they know I could be away at work or out shopping.

To the OP, is it possible to take one full day off and then set aside a specific time on the other day to answer questions?  If your answers are likely to lead to more questions, tell them you're only available between certain hours on the weekend, or that you have limited access to your computer on weekends, or that in order to save your marriage & family you've decided to spend only limited time on business matters on the weekend.  You could put something to this effect in your listings.  I've seen plenty of stores that have a message in their listings to say they only answer queries in business hours.  If you make it humorous it might actually have more impact, eg. my wife said she'll divorce me if I don't spend the weekends at home with her, so I'm not available to answer questions between ... and ...  Or, "I'd like to see my kids grow up so I confine my work to business hours now."  I think people will respect you more for taking time off than if you were there all the time.  Invite them to walk all over you and a lot of them will!