Search engine optimisation is a gradual process like Investment, so its not for fast results for sure , different businesses have different level of competition and different level of relevancy on internet and that’s one cannot say about time one business will be needing. In most of the cases agencies take 6 - 7 month to an year for a business to increase organic traffic but this is just an estimate not a fixed thing .
Yes you should definitely take SEO service because in many cases you need not to utilise full budget for SEO unless until you want it for example if you want to rank on 5 key words you will drive all traffic of the searches on all those 5 keyword but lets assume you started ranking already on 2-3 keywords and suddenly leads and conversions increases for your business, you can stop your SEO service or switch to a slowpaced low rate SEO until your competition is relevancy increases?
Fixed plan is designed for clients who can’t afford customized plan, benefit is it fixed plan can be taken by small business’s drawback is it is slow paced and can take more time. On the other hand Customized plan is more accurate and is Fast paced , draw back is its little costlier than fixed plan.
