Maximum Amount of Strong Tags?

It's got to be natural. Do you mean you emphasize each time your
keywords get mentioned?

I don't think there is a limit. But use it as the heading of a paragraph
or section. If you have 20 sections, you could do it 20 times. But even
that might not look right if they are 1-2 sentence sections.

Remember, when all else fails, think about how you, the visitor, would
navigate, read, and interact with your page. A lot of people forget
this. If it makes sense and flows, there really is no limit.

I use the bold and <h1>.....<h6> headings only for the title and
section intros. Normally 2-3 sections, of about 2-3 paragraphs of
about 6-7 sentences. That's just my overall average. Not saying that's
how it should be done. I never worry about using a keyword too many
times. I use them as often as I can, but they have to fit with the flow.

I never emphasize, strong, bold, or whatever, a keyword that is in
normal content sentences.

I do use it also for the heading of my internal link navigation list.

Paul

You're doing it wrong.

Write for your readers, not search engines.

Get your keyword in your page title, H1 header, and a couple of times in you content. Use bold once or twice if you're feeling feisty. Throw in a picture or two and get your keywords in the ALT tag.

Using your keyword 20 times in a 500 word article isn't going to improve your rankings and isn't going to fool google.

Keyword stuffing is sooooo 2005 and keyword density is a bunch of poo.