While the 1/8" Polyurethane tubing is treated to be UV resistant, ultimately the UV in sunlight will cause the tube to deteriorate.  The first signs of deterioration will be tiny pinholes.  It is impossible to say how long exactly the polyurethane tubing will last, and it does unfortunately vary with the degree of exposure, but longevity of 12 months, and even up to 5 years has been experienced. The key to longevity is limiting sunlight exposure to a minimum.  The 1/8" tubing is, being flexible and small, easy to hide inside and behind vinyl sidings, or under roof eves, and even buried for runs between the house and the shed, say.
Polyethylene tubing, like the 1/4" tubing typically used in drip and spray irrigation systems by a number of suppliers, tends to have a superior UV resistance than polyurethane. Therefor if there are particularly exposed runs where exposure to sunlight cannot reasonably be avoided, it is recommended to run this part of the route in 1/4" polyethylene tubing and reducing up to it, and/or down from it using the available 1/4" x 1/8" reducers. There is no harm, or change to the way the Plant Booster system works, if the reticulation system includes a mix of tubing sizes.  Because the water flow rates are very slow, pressure drop is basically negligible, and therefor not an issue.
The picture below illustrates an installation on a local restaurant patio, where the 1/4" x 1/8" reducer can clearly be seen just before the Plant Booster device.
This is also the recommended approach at commercial installations, where existing systems irrigation that are being upgraded to Plant Booster watering management typically already have 1/4" tubing installed.
For retrofits, there is a double benefit in that the existing tubing need not have to be removed, but only has to be checked for leak-tightness.
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