Code to get PMPro Gift Levels and PMPro Set Expiration Dates to play together nicely.

pmpro_after_checkout_gift_level_set_expiration.php

/*
	Define Gift Levels
*/
function init_gift_level()
{
	//define the levels
	global $pmprogl_gift_levels;
	$pmprogl_gift_levels = array(
		4 => array(                     // "Purchase Gift" level ID
			'level_id' => 1,            // Membership Level ID of the gift membership level.
			'initial_payment' => 0,     // The initial payment for the gift membership level.
			'billing_amount' => 0,      // The recurring billing amount for the gift membership level.
			'cycle_number' => 0,        // The number of billing cycles for the gift membership level.
			'cycle_period' => '',       // The billing cycle period. Possible values are "Day", "Week", "Month", and "Year" (without the quotes).
			'billing_limit' => 0,       // The billing cycle limit for the gift membership level.
			'trial_amount' => 0,        // The trial amount for the gift membership level.
			'trial_limit' => 0,         // The number of cycles the trial should last for the gift membership level.
			'expiration_number' => 1,   // The number of "experiation_period"s before the gift membership level expires.
			'expiration_period' => 'Year'   // The duration of the period used by "expiration_number". Possible values are "Day", "Week", "Month", and "Year" (without the quotes).
		)
	);		
}
add_action('init', 'init_gift_level');

/*
	If a gift level is purchased, copy the set expiration date if applicable.
*/
function pmpro_after_checkout_gift_level_set_expiration($user_id)
{
	global $wpdb, $pmpro_level, $pmprogl_gift_levels;
	
	//only if the set expiration dates plugin is active
	if(!function_exists('pmpro_saveSetExpirationDate'))
		return;

	//check if we're checking out for a gift level
	if(!empty($pmprogl_gift_levels) && !empty($pmpro_level) && !empty($pmprogl_gift_levels[$pmpro_level->id]))
	{
		//get last gift code
		$gift_codes = get_user_meta($user_id, 'pmprogl_gift_codes_purchased', true);
				
		//not sure why we wouldn't find any, but just in case
		if(empty($gift_codes))
			return;
			
		//get the last one
		$last_gift_code = end($gift_codes);
				
		//again, just in case
		if(empty($last_gift_code))
			return;
		
		//look for a set expiration date
		$set_expiration_date = pmpro_getSetExpirationDate($pmprogl_gift_levels[$pmpro_level->id]['level_id']);
				
		//save it
		if(!empty($set_expiration_date))
		{			
			pmpro_saveSetExpirationDate($pmprogl_gift_levels[$pmpro_level->id]['level_id'], $set_expiration_date, $last_gift_code);
		}
	}	
}
add_action('pmpro_after_checkout', 'pmpro_after_checkout_gift_level_set_expiration', 20);