deciding the optimum url length for search engine benefits

Selecting the most appropriate url formats for search engines: 

How doe a search engine decide the "  length of  the optimum size of url which is considered to be search friendly ?

While its true that search engines does give a fair amount of importance for the url specification, SE also are quite adept to  understand  and  interpret regular long urls with numerous hypens   and the extent to which webmasters  can use them for " spamming it " ( for example some seo webmasters at the sound of getting too excited and may use words like buy-this-awesome-product-iasshumiort-html.as an actual url .) This only sends out the signal and tells the search robots and give them the sound of trumpets" telling them to discount the entire post/ url as a spam .. as its the result of an over excited adolescent seo webmaster

So how do you show the search engines about the content and its url parameters by ensuring you do this just the right way ?1) Describe your  content :  if a user can  make an accurate guess about your content  by looking at the address bar, you have done your job2) Use static URLs: dynamic url's are harder to index for both search and users
3) Descriptors not numbers:  never use  a random 1234 numbers or a set of numbers..when you can use brand/name etc4)use lowercase: Although urls can accept both upper and lower always desist from using Uppercase