2. How long will Preschem’s Preservatives last?

This is subject the the environment the timber is in and how much persistent moisture is present, but for most normal situations where the preservative is expsoed to the weather unless otherwise stipulated:

Timber Preserver: 4-5 years
No-Rot: 4-6 years
No-Rot Gel: 4-5 years (note that exposed exterior timber must be sealed with a quality exterior paint, otherwise the expected life will be 6-8 months)
Clear Wood Preservative: 12 months
Heavy Oil Preservative: 4-5 years
In-Ground Paste: 4-5 years