Regarding peristaltic pumps

[nlreefguy]

Just wondering what the lifespan of dosing pumps is? I have two pumps from reefdosingpumps.com tht now are having trouble turning when hosing is connected to them. They will turn no problem when there is no resistance. What's the problem here? Is there any maintenance I can do to help? These pumps are quite old now, both of them are over 5 years old. Do they need to be oiled or something????