About how long is a lye relaxers shelf life?

[MystiqueBabe]

I am thinking of switching to lye relaxers and since I am a avid stretcher I will only be using the lye relaxer probably 3 or 4 times a year. How long is their shelf life or should I just stick with box relaxers that way when I am ready to retouch I won't have to worry about it expiring.

Thanks in advance.