How Long with 3UK SIM Work for Incoming Calls Without a Topup?
 

I bought a Three UK SIM off of ebay, sent to me in the US. I noticed that without any topup, incoming calls go through (free USA roaming, so no charge for incoming calls to the US.)

Anyone know how long I can use the SIM for free incoming calls without a topup before it gets shut off by the carrier?

I believe that you have to make a chargeable call or text every 90 days. Check the T&C as it might be 180 days. I do it every 90 to be on the safe side.