Would an 80gb data plan be enough?

[Andrew]

I ask this as my parents contract with vodafone for our adsl ends in a few months and my mum and me were looking at better options.
Right now we are on a "What ever speed your adsl line can take and 100gb" plan
We had a look at orcon's VoIP 80gb VDSL plan. VoIP would be great in a way as the phone SOMETIMES (I think i might have fixed it now as it hasnt gone out for a few days now) disconnects the dsl. The main point is that would 80gb be enough?
My mum and me are the only 2 who use the internet, she plays games on her ipad (online ones), surfs the net, facebook and skype.
I like the internet for downloading and playing games (e.g steam)
We need voicemail and unlimited nationwide calling (I live in new zealand so don't go on about US isp's like at&t cause it doesnt exist here) with nationwide calling and voicemail, caller ip and caller waiting added it comes to $109NZD a month.
The unlimited plan is $133 for vdsl and the extras
Orcon is by far new zealands cheapest isp if you are talking price/speed ratio
My average monthly usage is anywhere from 2ogb to 88gb a month
We would have gone for fibre as thats much better and cheaper but where I live in the country it has been determined its going to be installed during 2019 which is ages away!!!!
Oh and before I forget we pay right now for:
100gb max adsl speed
unlimited new zealand wide calling
caller id
voicemail
= $90NZD
Thanks

[?]

From my experience I know the following:

1. Playing a 5 minute video on fb will take 30-100 MB of data.
2.An average fb user who uploads and watches videos uses about 40 GB a month(Source: my friends and I checked our usage a few weeks ago)
3.Each session of an online game will take 50-100 MB
All in all, the plan is OKAY. But if you use torrents to download stuff, then it is definitely not enough. Judicious usage of internet will make this plan worthwhile.