Sometimes I feel limited in both thought and innovation and it always comes to mind that it's time to move on. Maybe in a new job I can improve my skills as an engineer and find better salaries as a result. 
If you continually get better at your job as you get more experienced over time, and they dont pay you more, then they clearly dont see your experienced as valuable and you should demand a raise or look for an alternative. This is only the case if your not happy with your job which your first sentence indicates.
even if you're enjoying your work, I believe that a raise also shows you that your company values you and your work.
yes yes, but if i really enjoy my job, and i ask for a raise then they say no. im still not going to quit or start looking for alternatives because i really love the job that im doing then. Ill ask for a raise again in the future.
I don't know. I imagine you love what you do, but if you feel you're not valued, would you stay there?
I care more about how i feel, rather then what others think about me. I dont care of my coworkers want me dead, if im enjoying my job, why would i want to go to a different job.
The maximum you should stay is five years, but beyond that you'll only be making money for them and not for yourself.