How much is too much?

I am part of a five author box set entitled "Regency Quintet– Valentine Edition". The idea behind this was to introduce readers to different authors in a genre that they already enjoyed. We have managed to get this publication into the bestseller charts on both sides of the Atlantic – although it reached number two in the UK and only seventy-two in the US.
What occurred to me during the media campaign we were involved in is – how much is too much promotion?

£1.50 Amazon only.

I tweet once or twice a day but only do promotional tweets when I have a new book out – which is once a month. However, as no doubt you have noticed, 95% of what appears on twitter is promoting books/blogs/book tours etc.
Did anyone who read these actually by the book? We had plenty of retweets/favourites etc, but whether it increased our sales I have no idea. What I do know that, as a reader, I switch off if I am bombarded by constant reminders that book has yet another five-star review, has sold shed loads of copies, has won an award.
I am guilty of putting up posts on Facebook myself of the above variety. However, I think my posts on my normal Facebook page are 80% at least of general wittering. Things are different on my author page as here everything is book related – but it can be talk about what I'm doing/where I'm up to in my current book – or information about covers and sales.
What do you think? Do you immediately visit the blog/author page or download the book when you see it mentioned on Facebook? I tend to buy books through recommendations from friends – which I suppose must mean the promotional post has worked.
Although I no longer read posts by some writer friends when I scroll past them because they are always promoting their books/mentioning another five-star review/or a book tour – never anything personal or interesting or commenting on anyone else's activities.
It has been suggested that writers should contact reviewers and ask for reviews – that's something I have never done and don't intend to start doing now. I know having X number of five-star reviews improves the algorithm on Amazon – but I prefer my reviews to appear organically – even the one star reviews I sometimes get from our American friends.
I have a bestselling writer friend who does no publicity or promotion at all – she puts up a new book every four weeks and leaves her readers to decide whether they're going to buy it. Currently she has eight titles in the bestseller list – which rather speaks for itself. Good writing and great stories don't need constant promotion.

£1.50 Amazon/KU

£2 - Amazon/KU

My latest regency, Lord Ilchester's Inheritance, which came out a couple of weeks ago is already in the charts. I did my usual round of posts on half a dozen loops that I belong to and that was it. Lady Eleanor's Secret came out in December and had exactly the same promotion but has sold only a handful in the US although it's selling well in the UK.
I have no idea whether adverts/promotions/media tours etc do more than irritate the recipients without gaining actual sales. I would be interested to hear your views.

Fenella J Miller