Is it allowed for a person to perform Tawbah whenever they feel guilt over their sins, such as wasting time or not seeking forgiveness, on a weekly basis, or would this not be viewed as sincere repentance?
Seeking forgiveness is required always especially after committing a sinful act or remembering it. It can be a daily process especially before and after obligatory Prayers and in the night especially on the last part of the night (Sahar time). It can be also every week on the Eve of Friday (Lailatul Jumu'ah) or on every Friday.
Wassalam.