Do you have to activate the FiOS CC within days of getting it?

I just went to my local Verizon FiOS store in Yonkers and got 2 CC's. The lady at the store told me that I had to activate the 2 CC's soon, or I would lose the activation. I haven't bought a TiVo setup yet, but I wanted to be ready with the CC's at home. I was originally going to order these online, but I didn't want to pay the $25.00 shipping charges. I called the Verizon 800 number and they placed an order so that I could pick the cards at my local store for free. I received 2 Arris cards and a receipt with an activation code. I am thinking about purchasing a TiVo setup in the next couple of weeks. Could I activate these cards as late as mid June, or would I have to get new cards if I wait that long? Thanks a lot for any help.