Sales Pitch & Readability vs Keyword Optimization
The title plays a significant role for the keyword optimization, as well as for the content optimization.
On the one hand keywords within the title are weighed stronger than any other input areas. On the other side the title's mere content offers the first opportunity to get customers interested in a product, and often no further opportunity will follow.
It is therefore all about finding the right balance between putting as many relevant keywords into the title and adding more sales pitches.
Balance through Keyword & Product Analysis
To find this balance, a thorough keyword and product analysis is required.
The keyword analaysis, for instance, could be about prioritizing the keywords by search volume (demand) or search results (competition).
For the product analysis it is important to understand the product's USP, as well as which problem it solves or advantages it creates. To find answers to those questions it is recommended to go through the reviews of the product (as well as competitors), in order to understand which aspects are the most important to customers.
High Influence on Click-Through-Rate (CTR)
Along with the main product image, the title arguably has the biggest influence on the CTR in the searchresults. The product's USP should therefore be made very clear in the title.
On a technical side, it is important to realise that the title is clickable. This means a longer title will offer a larger click area, which will also lead to a higher CTR.
Limitation of 250 Characters
All characters that follow after position 250 will be weighted equally as the backend searchterms. It is therefore not recommendable to use all of the 500 characters available for titles, as too many keywords can also harm the "readability" of your titles.
Pro Tip: On mobile devices only around 70 of the title's characters will be visible, so make sure to place your most relevant keywords and the biggest selling points at the start of the title.