Is a fifth weekly paycheck a bonus, or have I just budgeted as though it didn't exist?

My pay is $520 a week, and my monthly plan starts with four payments: $2,080. In a month with five paydays, the extra $520 makes me feel unexpectedly rich.

I usually finish the four-payment plan with about $80 unallocated. This time I wanted to use the fifth payment for a weekend with friends. My partner pointed to the annual costs that don't sit in my monthly list: an equipment membership and several family occasions I already know about.

I agree those costs need money. I'm less happy with the way a predictable payment has become either 'free weekend' or 'you forgot to budget properly.' I've treated previous fifth payments differently depending on whatever was most tempting that week.

Would you assign them in advance to annual costs, include them in a yearly plan and smooth the amounts out, or deliberately keep part for something enjoyable? I want a method I can repeat without turning every month with five paydays into an argument about a windfall that wasn't really a surprise.