You can use them for an upgrade voucher to Europe (200 points), or to the US and add money (700 points, so you'll need to add $180).
Note that in order to use the voucher you'll need to book a flight in the higher buckets (M/S/Y to upgrade to C, I/C to upgrade to F).

Once you issue the voucher it's good for a year, so you "earn" an extra year for your points. There's no way to prevent them from expiring.

Alternatively, you can use the points for discounts on LY's last minute fares. However, that's not such a good option as the point value there is quite low.

Lastly, you can always donate your points for a good cause. See http://www.elal.co.il/ELAL/English/M...ions170210.htm