I turn off my cell data connection all the time. Often times I will do it at home where I have wifi. Then I will turn it off at work so that I am not bothered by various notifications and because the signal is not the greatest. The biggest issue is when I get MMS messages and I have to turn the data back to download the attachment. I don't get enough of those for it to be an issue.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
My understanding is that anything you do on WiFi does not use up your data package at all. This is because the information is not going over your 4G or 3G cellular connection, but through the Internet connection to which the WiFi is linked. You might want to try just using your data connection for awhile and monitoring it as you go if possible. My phone has a little My Verizon Data widget that shows how much of my 4GB I've used up in the current billing cycle. If you can use that, and you see that the data allotment is being used up faster than the days of the month, then you could switch to WiFi whenever possible.
When you are on WiFi you are not using your cellular data (for the most part). Like Ann154, I turn off my cell data all the time when I am in WiFi environments....I actually generally only turn it on when I am expecting to be away from home/office for a while. Otherwise its all WiFi for me and I generally only use about 125MB per month doing anything and everything I want on my phone.
One thing not mentioned here is battery usage with wifi vs data. You should experiment to see which uses more battery. Battery usage can depend on the strength of of the wifi and data signals. If you have a strong 3G/4G connection, it can use less battery than wifi, and the reverse can also be true. If you have a weak data signal, it can take longer to download that wifi and thus use more battery. Sometimes it may take longer to find a wifi connection, which also uses more battery.
One thing that I find with the WiFi vs. data, is that if I'm using my WiFi at work (a school), I am subject to the same Internet blocking from our network/IT deparment as the hard-wired and/or wirless computers; it reduces the very convenience for which I want the app.
i would suggest what dave in decatur does. use the my verizon data widget and you'll always know "about" how much data you have consumed (it's not exactly accurate, but pretty close). wifi does not count against your data. if you are unfamiliar with data usage and what consumes more or less data then here's a real generic idea of it:
-streaming music or (especially) video will eat it up (if you are on a limited plan then always use wifi for this stuff if you can)
-downloading music or video will eat it up
-browsing and most apps that use data (facebook or games that are played on the network like words with friends), only use very little data
if you montitor it closely for a couple of months then you will have a real good idea as to what type of user you are and how much data you consume. "most" people wont use 4gb's unless they download or stream music or video often. i'm a fairly heavy user, but only consume about 1-2 gb's per month (i rarely stream video unless i'm on my home or work wifi network).