If you're going to use DI vessels, and you have the space, it's really worth thinking about buying two vessels and using them in series as this can extend resin life substantially
When you only use a single DI vessel, you have to replace the resin as soon as the TDS level on the output starts to rise - but you could continue using the resin for much longer even though the TDS level of the output would continue to rise it would still be substantially below the input level
If you use the output of a DI vessel to feed into a second DI vessel, the first vessel can continue treating water (and using up its resin) for as long as it's supplying reduced TDS level water to the second DI vessel. The resin in the second vessel lasts substantially longer as it's being fed with partially treated water.
Once the output from the second DI vessel starts to rise, you replace the resin in the first DI vessel and swap the vessels around so that the untreated water goes through vessel 2 first and then feeds into vessel 1
e.g.
Start with
Tap -> DI 1 -> DI 2 -> Hose
When TDS of the output starts to rise, this indicates resin in DI 1 is fully used, resin in DI 2 is partially used, so replace resin in DI 1 and swap connections to
Tap -> DI 2 -> Di 1 -> Hose