esp_timer_get_time starts counting from 0 at startup / wake from deep sleep. It increments every 1uS

int64:
0x0000000000000000 to 0x7FFFFFFFFFFFFF
9,223,372,036,854,775,807 uS
9,223,372,036,854 seconds
153,722,867,280 minutes
2,562,047,788 hours
106,751,991 days
292,471 years

Using esp_timer_get_time to time things

#include "esp_timer.h"

static int64_t HeartbeatLast1msTime = 0;


	while ((esp_timer_get_time() - HeartbeatLast1msTime) >= 1000)      //esp_timer_get_time() provides uS since startup. int64 x 1uS = 292,471 years before rollover
	{
		HeartbeatLast1msTime += 1000;
	}