Do not allow membership renewal unless the level is expiring in the next 45 days.

my_pmpro_is_level_expiring_soon.php

<?php
/**
 * Do not allow membership renewal unless the level is expiring in the next 45 days.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

/**
 * Consider a level to be expiring soon only if there's 45 days or less until expiration.
 */
function my_pmpro_is_level_expiring_soon( $r, $level ) {
	if ( ! empty( $level->enddate ) ) {
		$now                   = time();
		$expiration_date       = $level->enddate;
		$days_until_expiration = ceil( ( $expiration_date - $now ) / ( 60 * 60 * 24 ) );

		if ( $days_until_expiration > 45 ) {
			$r = false;
		} else {
			$r = true;
		}
	}

	return $r;
}
add_filter( 'pmpro_is_level_expiring_soon', 'my_pmpro_is_level_expiring_soon', 10, 2 );

/**
 * Redirect from Checkout page to the Levels page if the level is not expiring soon.
 */
function my_pmpro_checkout_redirect_non_expiring_soon_levels() {
	// Make sure PMPro is active and that we are on a checkout page.
	if ( ! function_exists( 'pmpro_is_checkout' ) || ! pmpro_is_checkout() ) {
		return;
	}

	// Logged in users only.
	$user_id = get_current_user_id();
	if ( empty( $user_id ) ) {
		return;
	}

	// Get checkout level.
	$pmpro_level = pmpro_getLevelAtCheckout();

	// Bail if the user does not have the checkout level.
	if ( ! pmpro_hasMembershipLevel( $pmpro_level->id ) ) {
		return;
	}

	// The user has the checkout level. Bail if it's expiring soon.
	$level = pmpro_getSpecificMembershipLevelForUser( $user_id, $pmpro_level->id );
	if ( pmpro_isLevelExpiringSoon( $level ) ) {
		return;
	}

	// Redirect to the levels page. Adding a query parameter so we can show a message on the levels page.
	wp_safe_redirect( add_query_arg( 'norenewal', '1', pmpro_url( 'levels' ) ) );
	exit;
}
add_action( 'template_redirect', 'my_pmpro_checkout_redirect_non_expiring_soon_levels' );

/**
 * Show a message on the levels page.
 */
function the_content_add_non_renewal_message( $content ) {
	global $pmpro_pages;
	if ( ! empty( $pmpro_pages ) && is_page( $pmpro_pages['levels'] ) && ! empty( $_REQUEST['norenewal'] ) ) {
		$content = '<p><strong>You must wait before renewing your membership.</strong></p>' . $content;
	}

	return $content;
}
add_filter( 'the_content', 'the_content_add_non_renewal_message' );