Thanks for your post, and good luck on that GMAT!! Stanford is certainly an inspiring and ambitious goal, as it's the most competitive program out there (with a smaller -than-average class size, tons of applicants and high average GMAT), but if you have your heart set on it as the program for you then I do encourage you to go for it as your passion for the program can hopefully shine through.
And adding a few other school options to your list would be recommended as it will be a reach program (for most applicants!).
The average work experience at Stanford last year was 4.2 years, so right about what you have, so certainly adding one more year shouldn't be a problem as 4.2 is just the 'average', if that helps your profile and ability to submit a strong application.
I would just suggest if you apply next year, really think in the coming year about how you can show RESULTS that you contributed to at work; how you can show initiative and leadership; how you can go above and beyond what is expected of you and truly make an impact. Those are key areas that would help you stand out and get noticed by the schools. Good luck !
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