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Hi Allan

You don't need to update the sitemap if the content has changed but the URL of the page remains the same. The only time I update sitemaps is 1. if there are new pages and 2. if we remove pages. If you don't update the sitemap after you remove a page then you'll get 404s (e.g. a busy e-commerce site when products are sold out and not going to be restocked, you'd remove the page).

How does anyone know what will be spammy in 1 to 3 years? With that logic you might as well disavow all links.

I actually use this technique on my own and client sites and it's very effective. A word of warning though, this is not white hat SEO and as such I do disclose this fact to clients.

I don't 301 the expired domains because there would be little point in doing so. You need those expired domains being seen as separate incoming links.

I set my expired domains up as mini sites and have original content written for them. The content then has a couple of links through to my main site. They go on completely separate hosting accounts with a different C block IP address i.e. don't put them on your own hosting account because they will not count as incoming links from separate C block IP addresses (important). Also hide your whois information.

Hi

If it's a small site you could manually update the expired job to say that the job is no longer available 'but you might like the following' and link to similar jobs. It would keep the visitor on your site and perhaps lead them to something they'd be interested in.

If you want to automate it I'd set up a standard 404 with a site search in it to recommend searching further (as opposed to losing the visitor completely). Not sure why it wouldn't be possible to set up a 404?

I've seen so many sites with blogs and social media accounts which are hardly ever updated e.g. blog posts that are more than 6 months old. It really makes you think they don't look like they could be bothered. I think seeing that a company is active on social media etc gives the impression that they are active and therefore makes your site look more up to date. I therefore don't think it's just the content quality that's relevant.