1.) Site is covered with tables
Earlier websites were mostly built using tables. This is not a very SEO friendly approach. This is because it is difficult for search engines to read the content. These days website are tableless and SEO friendly.
2.) Programmer intervention needed for every little change
CMS driven websites are in boom. A CMS or Content Management System gives website owners the ability to change the content of the website themselves. Consider getting your website revamped if you have to approach your web designer for every single small change.
3.) Code Piled up
This happens when the code offered to you is bad and heavy or if you approach web designers (same or different) to make constant changes onwebsite over the period of time. The result is heavy code that is piled up by these updations. It is at this time you must consider a website revamp.
4.) Responsive and Mobile Friendly Websites
Statistics reveal that the number of users checking a website on mobile has increased. If your website does not display appropriately in different devices like tabs and mobiles, then you should probably consider a website revamp.
5.) Lengthy Flash Integration