My current 506 hydrominders for all my chemicals are around 10 to 12 years old now and I have replaced the valve parts over the years. But when I was talking to a Blendco salesman he asked me how old they were and he said that they should be replaced. I am curious as to why he said that. Are there any other parts that may wear out from normal wear and tear over the years? Is it beneficial to start upgrading my hydrominders to the 511 with the push in meter tips because they now have a wider range of ratios and it might save me money in the long run on chemical?