Budget
How long your assets will last in retirement is a function of how much money you need to live on. Plan a budget for anticipated financial needs during retirement. Some expenses will be less as your work-life ends, but some expenses may be more such as healthcare costs.
Insurance (other than medical)
Your insurance needs will likely change in retirement. Perhaps you will be driving less and can get a discounted rate for car insurance. Review all existing insurance policies to determine if they meet your needs in retirement, or could premiums be reduced.
Financial advisor
You may have been your own financial advisor up to now. The rules of the game change in retirement, so having professional advice may be prudent. Some investment companies are offering financial advisors at discounted fees. The savings can be considerable.
Estate planning
If you have estate planning documents, they should be reviewed as you approach retirement. If you do not have estate planning documents, you need them now more than ever. It is prudent to have competent legal counsel prepare these documents.
Considerations: Distribution of assets as you wish, probate vs. non-probate assets, beneficiary designations, children from prior marriages, special needs of heirs, inheritance and estate taxes, charitable giving
Related documents: Will, living trust, financial power of attorney, advance healthcare directive (living will), medical power of attorney