It also depends on what sites you are using in your tiers. For example if your first 3 tiers are wordpress pbn links, then you know you will have 100% indexing rate on the 3 tiers. Then adding a further 3 tiers of ser links would make a 6 tier linking structure.
Going beyond 3 tiers of just ser links is going to be counter productive though, solely because of the indexing issues. A single link that is not indexed will stop the strategy from working.
If you don't have indexing issues with the links you build, then you can build as many tiers as you like....the more tiers you use, the more powerful the impact on rankings.
The way i see it is, a tier 1 link with no inbound links is unlikely to increase in page authority and have minimal impact on rankings. So it will always be a weak link. Which means even a tier 3 link with no inbound links is a weak link.
But within a 3 tier structure, the page authorty of the tier 1 link will increase significantly, as it has inbound links, and those tier 2 links also have inbound links. That really is the sole goal of tiering....to increase the page authorty of the tier 1 link.
I found two was more than enough with a quality indexer (Express Indexer gets my vote). Get the volume right and do one project per keyword and target a full optimised page(s) for those keywords.
Comments
As always you should test for yourself
However you'll probably have better results plugging your tier 3 to an indexer service rather than wasting resources on tier 4.
Going beyond 3 tiers of just ser links is going to be counter productive though, solely because of the indexing issues. A single link that is not indexed will stop the strategy from working.
If you don't have indexing issues with the links you build, then you can build as many tiers as you like....the more tiers you use, the more powerful the impact on rankings.
The way i see it is, a tier 1 link with no inbound links is unlikely to increase in page authority and have minimal impact on rankings. So it will always be a weak link. Which means even a tier 3 link with no inbound links is a weak link.
But within a 3 tier structure, the page authorty of the tier 1 link will increase significantly, as it has inbound links, and those tier 2 links also have inbound links. That really is the sole goal of tiering....to increase the page authorty of the tier 1 link.