After spending 3months rewriting an huge module for our many websites, initially estimated for 3weeks at most, I can say that it's easy to make mistake but also

After spending 3months rewriting an huge module for our many websites, initially estimated for 3weeks at most, I can say that it's easy to make mistake but also incredibly good for the company. - Mixing refactoring and new feature. - Introducing new technology - Changing behavior of old code that were not directly concerned by the rewrite ... Many things that should have been done after that. But, all I can say is if the company can handle this amount of work, it will always be a very good way to improve the quality and durability of the website. Because if you simply rewrite code, there is a big chance that your company will assign to you, new task that are not related at all and you will never be able to introduce these feature.