The rules in the faq [1]are very fuzzy on purpose, so I will just share my interpretation/opinion:
I think up to three reposts are fine, but I usually don't complain until the 5th or 10th repost. One per week is fine, I think the upper limit of tolerability is one per day.
Don't repost if the previous post got traction, If I have to pull a number out of thin air, something between 20 and 50 upvotes/comments/upvotes+comments
Your previous two post got a minimal traction but not too much. I think it's fine to repost it, but I'd expect even less traction. Try to use a more dry title, like "Show HN: Pingr – Uptime monitor" or "Show HN: Pingr – Know when your site is down before your customers do" or something like that. The name in the title is not mandatory, but I like it. Perhaps add a comment with more details and a personal history.
Sometimes it is easier to get traction here writing about an interesting problem you solved while making the site, for example how do you detect that it's a problem in the site and not a problem in your site, how difficult is to coordinate the distributed network of monitors, problems with spam or dos with the free trial If you meet an old friend and have to tell a funny/weird technical anecdote about your project, what would you tell?
Some feedback: The lifetime subscription is too long.
I think 'Show HN' is signalling to people that you don't think anyone would be interested in the content. It is like apologizing.
Make content people are interested in.
your show HN posts should be different in subject matter and should not be consecutive or sequential, or otherwise shove other postings off the page