High -quality backlinks are what that would stay for a long time. For instance, if you have done links through forum posting then it should remain as usual instead of getting removed or flagged.
do you offer seo services ? i have clients looking for these servicesIn my opinion, there are three pillars of SEO:
1 - On-Page SEO Optimization
2 - Content
3 - Backlinks
Each pillar is equally important to your success in your SEO effort.
The real question is the quality of each pillar, and for "Backlinks" relevancy is also extremely important.
Don't chase quick win and irrelevant backlink just for the sake of having a Link.
There are tons of resources available online on these topics, so my advice is to read and learn as much as you can.