@denrosh
Yes, I have taken advantage of the "special offer" from FindMyPast.
Only downside is that it is billed in one lump annually, ie 99 pounds and not the 8.47 per month.
To answer your question, there are absolutely no restrictions on the amount of usage.
Their website states that the offer is available for a limited time only, without actually stating a date of expiry.
It's certainly the cheapest offer from FindMyPast that I have ever seen.
I believe people have been complaing about the subscription costs.
Ancestry has had for a few years running a similar offer of all access for 89 pounds and also has the 1921 Census available.
Ask here on Rootschat for the current link to the offer
Rebel