3 UK expiration question
 

Is it true that 3 UK SIMs have unlimited validity after you have topped them up? Don't you have to do some kind of action every so often like send a text or whatnot so you keep your balance?

Three UK - No usage policy
 

Pay As You Go customers are required to use their account (whether it be chargeable or free, including Skype usage) once every 180 days, or "Three" reserve the right to terminate or suspend their service.

Simply make a free skype call. For example, call the echo test number: echo123

3 - Help & Support - Terms and Conditions

I don't believe the ordinary credit expires at all, and there are times when my old one hasn't been used for ages. I joined their WePay scheme (now discontinued) over 2 years after my contract ended and I switched to prepaid, with no credit added in between. Account now:

<TABLE class=my-usage><THEAD><TR><TH></TH><TH></TH><TH>Remaining</TH><TH>Valid from</TH><TH>Valid until</TH><TH>Expires</TH></TR></THEAD><TBODY><TR><TD class="left heading" colSpan=6>Credit </TD></TR><TR><TD class=left><!-- true This logic appended to block we pay reward items to ROI users -->Top-up credit </TD><TD class=left><!-- 11716891 --></TD><TD>£0.92 </TD><!-- PAIG Refresh 2009 --><!-- End PAIG Refresh 2009 --><TD>-</TD><TD>-</TD><TD>Won't expire </TD></TR></TBODY><TFOOT><TR><TD width=128></TD><TD width=54>Total</SPAN></TD><TD width=95>£0.92 <!-- PAIG Refresh 2009 --><!-- End PAIG Refresh 2009 --></TD><TD width=90></TD><TD width=90></TD><TD width=83></TD></TR></TFOOT></TABLE>