How long do the filters in a PST last?

[Merlin66]

three questions - three answers

1. Loss of contrast and "mushy" views. You need to remove the filter to accurately assess the extent of the loss.

2. No. AFAIK it's a gradual process of deterioration...the views just get gradually worse.

3. No. There's no way of repairing a failed filter. It must be replaced.

HTH