Visitor parking limitations

I just notice while activating a one-day permit that the ones I've bought expire some time in 2029 - I thought the point of the online permits was that they wouldn't expire like paper ones? 

Also, while I'm here, why is there no mechanism on the site to save or download the purchased permit as a record? I usually take a screenshot in case of future queries, as once the time has past there is no proof that that permit was correctly activated.

But I see you can still purchase up to 999 day permits in a year, which means the potential problem of 'selling on' has not been dealt with.