length of validity of french sim card

The validity is explained under the FAQ tab - please see below;

What is the validity on the credit and SIM card?

• Once activated a call or top up must be made within 90 days of activation or the last call to keep the SIM, credit and number active. After 90 days of non-use you will receive a message from Toggle reminding you to top-up. If you do not use or top-up the SIM for a period of 120 days it will permanently expire.
• Failure to do so means the SIM, credit and number will expire and cannot be re-instated or refunded.
• If you want to keep your foreign number and are not in the country, for example you have returned to the UK, you can pay £5.00 a year to keep the number. This can be done online via your Toggle account annually.