Some boilers don't like return water lower than 130-degrees, so what you have may be a problem in the first place. Your manual should say. It depends on the type of heat exchanger in the boiler. If the return water is too cool, you end up with condensation, and ruins it by rusting things out. Most of the useage of an indirect is based on the storage water being 140. Where I live, you MUST have a tempering valve on the outlet of the WH. You can set that lower (often 119-120 is recommended for a home). The response time to reheat and get the first hour draw is based on the incoming water generally at 180.
You'd normally set the WH indirect up as a priority zone. It depends on what your boiler does when a thermostat calls for heat. Often, that triggers it to go to the high setting. A priority zone means that when the WH is calling for heat, it stops trying to heat the house, so you get all of it for the indirect. This normally doesn't take all that long, and when finished, it returns to maintaining the heat for the house.