Summary.
Currently Zabbix is lacking consistency with item history storage period default values:

• Item created from Zabbix templates will typically have default history storage period value 7d, sometimes 1w, etc.
• Item created from Zabbix UI will have default item history storage period value 90d.

Large periods like 90d for items with frequent checks will have negative footprint on Zabbix performance (increased data processing and storage volumes).
In contrast small periods like 7d will not give enough insight on problem resolution, debugging when detailed monitoring data is required - due to business cyclicality comparison with previous weeks are required. E.g. this Monday vs previous Monday and Monday before that.

As a trade-off 31d is acceptable from business and technical aspects and could be used as a default value throughout Zabbix.
For common use cases where analysis on periods above 31d is required, trends are recommended.

User story.
As a user I want to create items for hosts,templates with consistent and meaningful default history storage period value: 31 day.

Task.
1. UI:

1.1. Modify host/template/prototype (incl. mass update, LLD Item prototype Overrides) item configuration screen "History storage period" default value to 31d.

2. Templates:

2.1. Modify all existing templates (which are included in Zabbix - host/template/prototype sections) item "History storage period" default value to 31d (if there was no specific business requirement to set different value).
2.2. Produce new templates with item "History storage period" default value 31d (if there is no specific business requirement to set different value).