If you stay without permission, you are holding over and will end up paying a daily rate greater than the monthly rent. Landlord can evict you at any time and charge you for costs and attorney fees too.
If you want to stay, arrange to have the lease convert into a month to month lease under the same terms, or set a new term of 3-6 months. Landlord may not go for this option if the lease will end during a bad rental season. You don't have to draw up a complicated contract -- just say "The one year lease will be converted to a month to month lease under the same terms after it expires. Either party may terminate the month to month agreement by giving the other party written notice at least 30 days before the next rent payment is due. The one year lease is hereby incorporated by reference."
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.
