Don't know about cold
oil blowing any hoses off, but the primary purpose of the thermostat is to prevent engine
oil temps from running too low, which is not good for the engine.
For example if the t-stat opens at 200F then until the
oil gets to 200F, its not circulated through the cooler (because it doesn't need to be cooled). Once the t-stat opens oil will flow through the cooler until it gets back down to 200F (or whatever the rated close temp is). You need to do some research on what you want you optimum oil temps to be for your engine and application before buying the parts.