Legal Question in Landlord & Tenant Law in California

What you describe might be considered estoppel. It means the landlord might not be able to claim that your rent is late because the landlord's always accepted late rent from you. The problem is that the landlord consistently has provided you with notice to pay or quit. It appears that the landlord has become tired of your payment of late rent. If there's a reason, maybe you can work out a settlement so that you can make up any expenses the landlord's incurred, and formally modify your rental agreement so that you would pay rent on a later date or in two parts(presuming your paychecks come in after the first of the month).