And if the situation is a little more urgent, we use the expression "It's high time" which means it's very important that this happens now - "It's high time we left - come on or we'll miss the train." Or again a parent might say to an older child - "It's high time you found a job, young man!"
So in summary -
"Let's go" is an informal suggestion or a polite instruction -
"It's high time" - is a formal statement that it is important that something happen soon or that something happen now.
And now - it's about time I finished this answer.
So in summary -
"Let's go" is an informal suggestion or a polite instruction -
"It's high time" - is a formal statement that it is important that something happen soon or that something happen now.
And now - it's about time I finished this answer.