For clarity, the 35 hours must be completed within 5 years of the start of the driver cpc (whether this has been acquired by 35hrs or Mods 2 and 4). So it is perfectly possible to start a 5 year period in, say, Nov 2017 with an expiry in Nov 2022. You could complete the 35 hours during, say, December 2017. You will NOT, at that point, receive another card. The information will be stored and the new card issued towards the expiry date of the original card. The new one will be dated Nov 2027.
When the system started (2008) it was different and many folks, me included, managed to gain an 11 year card. But that is no longer possible.
Hope this helps, Pete 