Try implementing the validation through an class implementing the IValidate interface for the content type instead. This may work for you https://world.episerver.com/documentation/developer-guides/CMS/Content/Validation/ 

Hi Scott,

Thank you for help on this.

Using IValidate interface this max limit warning will not be removed on switching tabs within cms but IValidate interface will be specific to that particular page if we are using it and can't be generalized(Correct me if I am wrong in understanding this one).

And can we pass the limit from model property? 

In the following code snippet max limit 2 is hard coded, can this be passed from model property?

public class ContentPageValidator : IValidate<MainSheetNavigationBlock>
    {
        public IEnumerable<ValidationError> Validate(MainSheetNavigationBlock page)
        {
            if (page.NavigationItems != null && page.NavigationItems.Count >= 2)
            {
                return new ValidationError[]
                {
                    new ValidationError()
                    {
                         ErrorMessage =  string.Format(
                             CultureInfo.CurrentCulture,
                             "{0} has {1} item(s) and cannot contain more than {2}.",
                            page.GetPropertyName(p => p.NavigationItems),
                            page.NavigationItems.Count,
                             2),
                         PropertyName = page.GetPropertyName(p => p.NavigationItems),
                         Severity = ValidationErrorSeverity.Error,
                         ValidationType = ValidationErrorType.StorageValidation
                    }
                };
            }

            return Enumerable.Empty<ValidationError>();
        }
    }