Depends how old the probes are. I would replace the probes every year or at least calibrate them to prolong there life but no longer than 2 years. Temp probes don't have to change. You can buy an apex with wvettthing for around $350-400 and it be one of the newer white labeled ones. I personally paid $270 for mine with everything but I got lucky but I did replace the pH probe which cost me $80. If your looking for an apex put a wtb apex in the wanted to buy section on here and within a day someone will come to you with a better price.