It is up to you. The idea behind Term is buy what you need for only as long as you need it since the money spent is gone. You should have a net worth over $1million in 10 years and hopefully $2 million by 20 years. So, why keep paying for life insurance you don't really need?
The idea behind two policies is the concept that from year 20-30 you are partially self-insured. Hence, Policy number 1 could be for 2 miilion Level Term 20 while Policy number 2 is for $1 milllion Level Term 30. Perhaps, you prefer it the other way around or like to spend all your money on cheap women and liquor?
There is nothing wrong with buying a Level Term 30 policy ONLY with a value of $3 million. But, I'd prefer not to waste my money on extra insurance that I don't need.