DIY 65 gallon RainBenchYour Rain Bench® should last as long as any wooden structure that you paint or seal (i.e. a deck, wood siding, garden shed).  It also needs to be placed on a bed of pea gravel or permeable paving so moisture does not sit against the base.  Even if it is not properly maintained and/or needs to be replaced in 5 or 10 years, it may only cost about $15 to replace the entire framework of one standard Rain Bench®